thai geoscience journal

THAI

GEOSCIENCE

JOURNALVol. 2 No. 2 July 2021

ISSN 2730-2695

NEW NORMAL

Published by

Department of Mineral Resources

Geological Society of Thailand

Coordinating Committee for Geoscience

Programmes in East and Southeast Asia (CCOP)

Editorial CommitteeHonorary Editors

Advisory Editors

Editor in Chief

Dr. Apsorn Sardsud Department of Mineral Resources, Thailand

Associate Editors

Editorial Secretary

Department of Mineral Resources, Thailand

Ms. Cherdchan Pothichaiya

Mr. Inthat Chanpheng

Ms. Jeerawan Mermana

Mr. Kitti Khaowiset

Mr. Kittichai Tongtherm

Ms. Kunlawadee Nirattisai

Prof. Dr. Che Aziz bin Ali

Prof. Dr. Clive Burrett

Assoc. Prof. Dr. Kieren Torres Howard

Prof. Dr. Koji Wakita

Dr. Mongkol Udchachon

Prof. Dr. Punya Charusiri

Dr. Toshihiro Uchida

University Kebangsaan Malaysia, Malaysia

Palaeontological Research and Education Centre,

Mahasarakham University, Thailand

Kingsborough Community College & The Graduate Center,

City University of New York (CUNY), USA

Faculty of Science, Yamaguchi University, Japan




Coordinating Committee for Geoscience Programmes

in East and Southeast Asia, Thailand (CCOP)

Ms. Paveena Kitbutrawat

Ms. Peeraporn Nikhomchaiprasert

Dr. Puangtong Puangkaew

Mr. Roongrawee Kingsawat

Mrs.

Ms. Thapanee Pengtha

On the cover

1) Combined positive and negative data for source crater location. Greener areas = higher probability.

Yellower areas = lower probability. Red / orange areas = no probability. (Aubrey Whymark , p.22, fig. 23)

2) Bird-Feather in Khamti amber (photomicrographs by Thet Tin Nyunt; dark field, 40×)

(Thet Tin Nyunt et al., p.68, fig. 9)

3) Radiolarian SEM photos of Mississippian chert from southern peninsular Thailand. All scale bars

indicate 100 μm. (Katsuo Sashida et al., p.77, fig. 5 )

Sasithon Saelee

Dr. Sommai Techawan

Mr. Niwat Maneekut

Mr. Montri Luengingkasoot

Dr. Young Joo Lee

Department of Mineral Resources and





in East and Southeast Asia, Thailand (CCOP)




Dr. Dhiti Tulyatid

Prof. Dr. Katsuo Sashida

Prof. Dr. Nigel C. Hughes



in East And Southeast Asia, Thailand (CCOP)Mahidol University, Kanchanaburi Campus, Thailand

University of California, Riverside, USA

Department of Mineral Resources and


THAI GEOSCIENCE

JOURNAL

Vol. 2 No. 2

July 2021

Published ByDepartment of Mineral Resources • Geological Society of Thailand

Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP)

Copyright © 2021 by the Department of Mineral Resources of Thailand

Thai Geoscience Journal website at http://www.dmr.go.th/tgjdmr

Preface

The Thai Geoscience Journal, Volume 2 Number 2, online in July

2021, constitutes our One Year Anniversary issue. We propose continuing

our journal with several kinds of geological and geoscience objectives and

with an increased distribution. We need more co-operation with global

geoscience organizations. In this issue we welcome the Coordinating

Committee for Geoscience Programmes in East and Southeast Asia (CCOP)

as our co-organizers of the TGJ. We have the honor to warmly welcome Dr.

Young Joo Lee, Director of CCOP as our Honorary Editor along with his

colleagues to our editorial team.

The COVID-19 pandemic situation has changed the life and behavior

of people around the world. The New Normal has changed with most of us

working at home (WFH) along with social distancing. Our New Normal

geological life means that it is difficult and dangerous to go in the field. In

this situation, we will probably do more research about data management

instead and write articles from our stored data and then hopefully send the

results to TGJ.

We sincerely hope that the COVID-19 pandemic will soon be over and

bring back our life even though it will not be quite the same. We hope to find

a new way of life and learn to be happy again. Finally, we are pleased to

invite all geologists, scientists and researchers to publish in our TGJ.

Thank you very much.

(Dr. Sommai Techawan)

Director-General of the Department of Mineral Resources

President of the Geological Society of Thailand

Welcome to the Thai Geoscience Journal, Volume 2, Number 2. It is

almost one year since the first TGJ issue in July 2020. We have connected

our TGJ to the Coordinating Committee for Geoscience Programmes in East

and Southeast Asia (CCOP) as the co-organizer for this publication and we

will be working together on this and subsequent issues. We very much

appreciate the kind cooperation of Dr. Young Joo Lee, Director of CCOP,

and Dr. Dhiti Tulyatid, Regional Expert, CCOP.

This issue includes many geological articles from the CCOP’s annual

meeting and other researchers. The New Normal geoscience article

discussing Covid-19 and the world’s population is very relevant to the

current situation. The paper on the Australasian tektite forming crater is a

continuing theme from TGJ Vol.2 No.1 and may inspire researchers who are

interested in this new theory. This issue also includes various and interesting

articles such as the 3D geological mapping in Tokyo, Japan, mineral

resources studies (monazite and xenotime in Malaysia, and gemmology in

Myanmar), and Carboniferous radiolarians in Thailand.

Finally, we would like to express our appreciation to all of our TGJ

Vol.2 No.2’s authors for publishing your valuable articles in TGJ. As the TGJ

editor in chief, I would like to express my thanks to TGJ’s honorary,

advisory, associate editors, and reviewers for their kind support. Special

thanks are due to the editorial secretary team who have worked very hard on

every TGJ issue. We continue to strive to make TGJ a high international

standard journal and welcome all researchers to be TGJ members and to be

part of our geoscience community.

From the editor

Thank you very much.

(Dr. Apsorn Sardsud)

Editor in Chief

Thai Geoscience Journal

LIST OF CONTENTS


Vol. 2 No. 2

July 2021

ISSN 2730-2695



Printed: 2twin Printing tel +66 2 185 9953, July 2021

Any opinions expressed in the articles published in this journal are considered the author’s academic

Autonomy and responsibility about which the editorial committee has no comments, and upon which

the editorial committee take no responsibility

ข้อคิดเห็นของบทความทุกเรื่องท่ีตีพิมพ์ลงในวารสารฯ ฉบับนี้ถือว่าเป็นความคิดอิสระของผู้เขียน กองบรรณาธิการไม่มีส่วนรับผิดชอบ หรือไม่จ าเป็นต้องเห็นด้วยกับข้อคดิเห็นนั้น ๆ แต่อย่างใด

Page

A review of evidence for a Gulf of Tonkin location for the Australasian tektite source crater

Aubrey Whymark

1 - 29

The ‘new normal’ for geoscience in a post-COVID world: connecting informed

people with the earth

Steven M. Hill, Jane P. Thorne, Rachel Przeslawski, Rebecca Mouthaan, and

Chris Lewis

30 - 37

3D geological mapping of central Tokyo

Susumu Nonogaki and Tsutomu Nakazawa

38 - 42

REE and Th potential from placer deposits: a reconnaissance study of monazite and

xenotime from Jerai pluton, Kedah, Malaysia

Fakhruddin Afif Fauzi, Arda Anasha Jamil, Abdul Hadi Abdul Rahman,

Mahat Hj. Sibon, Mohamad Sari Hasan, Muhammad Falah Zahri,

Hamdan Ariffin, and Abdullah Sulaiman

43 - 60

Geology, occurrence and gemmology of Khamti amber from Sagaing region,

Myanmar

Thet Tin Nyunt, Cho Cho, Naing Bo Bo Kyaw, Murali Krishnaswamy,

Loke Hui Ying, Tay Thye Sun, and Chutimun Chanmuang N.

61 - 71

Additional occurrence report on early Carboniferous radiolarians from southern

peninsular Thailand

Katsuo Sashida, Tsuyoshi Ito, Sirot Salyapongse, and Prinya Putthapiban

72 - 87

Thai Geoscience Journal 2(2), 2021, p. 1-29 1


ISSN-2730-2695; DOI-10.14456/tgj.2021.2

A review of evidence for a Gulf of Tonkin location

for the Australasian tektite source crater

Aubrey Whymark*

Consultant Wellsite Geologist, Manila, Philippines.

*Corresponding author: [email protected]

Received 5 March 2021; Accepted 17 June 2021.

Abstract

Australasian tektites (AAT) occur across Southeast Asia, Australia, the Indian Ocean, and southwest

Pacific Ocean. AAT form the youngest and most extensive major tektite strewn field. Unlike other

tektite strewn fields, AAT have no known source crater. Review of the literature establishes that a

single ~ 43 km post-impact diameter crater exists, possibly significantly enlarged by slumping. The

obliquity of the impact that formed the AAT would result in a crater that is less pervasive in depth

but with greater downrange shock effects and melt ejection. Multiple lines of evidence, historically

viewed in isolation, were examined, concatenated, contextualized, and discussed. Tektite morpho-

logy and distribution; microtektite regressions; geochemical considerations, comparisons, and iso- -concentration regressions; lithological characteristics; age of source rock; and regional geological

considerations are reviewed. The source material is predicted to be an abnormally thick sequence of

rapidly deposited, poorly compacted, deltaic to shallow marine, shales to clay-rich siltstones of early

Pleistocene to Pliocene age. The impact likely occurred in a shallow marine environment. Forty-

two maps of positive and negative parameters are presented and overlain. These indicate the AAT

source crater probably lies in the central to northwestern Yinggehai - Song Hong Basin / Gulf of

Tonkin. This geochemically optimal setting is characterized by exceptionally high sedimentation

rates that explain the 10Be and Rb-Sr age discrepancy, the seawater signature, and apparent absence

of a crater by rapid burial.

Keywords: Australasian tektite, Gulf of Tonkin, impact crater, Pleistocene, Song Hong Basin,

Yinggehai Basin.

1. Introduction

Tektites are naturally occurring, holohyaline

macroscopically homogenous, droplets formed

by the melting and ballistic ejection of silica-

rich target rocks by large cosmic impacts.

Australasian tektites (AAT) form a young and

extensive strewn field covering over 10% of the

Earth’s surface. All major tektite groups, apart

from the AAT, have been geochemically

associated with terrestrial impact craters. AAT

have been extensively studied, drawing data

from diverse and disparate fields, each yielding

conclusion in isolation. This article attempts to

concatenate all available evidence to identify

the probable AAT source crater location.

2. Constraints

2.1 Presence of a Crater: All other known

tektite strewn fields are associated with craters.

The existence of silica-rich ballistic ejecta with

low-angle trajectories and velocities exceeding

5 km/s (Chapman, 1964) demonstrates a direct

transfer of energy, as opposed to an aerial burst

(Wasson, 2003), or impact plume (Wasson,

2017) scenario. An impact crater is concluded

to exist.

2.2 Single or Multiple Craters: The distance

of ejection can be related to crater size, which

in turn is a function of the mass and velocity of

the impactor (Elliott, Huang, Minton, & Freed,

2018). Other factors, such as obliquity of

impact and target composition, also influence

distance of ejection and are discussed in

Section 2.6. The distance between the most

northerly Indochinese macro-tektites and most

southerly Australian macro-tektites exceeds

8,500 km. The implication is that at least one

large impact crater is present. A thorough review

of the geochemistry of tektites (Schnetzler &

Pinson Jr, 1963), concluded that a random process

of formation or multiple separate impacts could

mailto:[email protected]

2 Aubrey Whymark / Thai Geoscience Journal 2(2), 2021, p. 1-29

be excluded. Nd and Sr isotopic variations

indicate a single impact event (Blum, Papanas-

tassiou, Koeberl, & Wasserburg, 1992; Shaw &

Wasserburg, 1982). Rare-earth elements (REE)

indicate a single reasonably uniform source

(Koeberl, 1994; Koeberl, Kluger, & Kiesl, 1985).

It is concluded that a single large crater in a

relatively homogenous source rock exists.

Associated smaller craters in the same source

rock cannot be excluded but are not required.

2.3 Age: AAT are 786 ± 2 ka based on 40Ar/39Ar

dating of tuffs at ODP Site 758 and relative

stratigraphic position to Termination IX (Mark

et al., 2017) or 788.1 ± 3 ka based on the 40Ar/39Ar age data from four AAT (Jourdan,

Nomade, Wingate, Eroglu, & Deino, 2019). The

impact occurred during a glaciation where the

continental shelf would be subaerially exposed

or covered by very shallow seas. The young

age means that geological evidence of the

structure could not have been eroded away.

The structure exists, even if buried. The recent

age of ejecta means that the tektite distribution

suffers little stratigraphic outcrop bias. Plate

tectonic shift of the crater and ejecta has a low

significance over this short period of time, but

in high resolutions should be considered.

2.4 The Crater Size: Utilizing microtektite data

and the methodology of Stöffler, Gault,

Wedekind, & Polkowski (1975), which is

calibrated to known impacts and thus has a high

expectation for accuracy, a post-impact crater

diameter of 32 ± 14 km is derived (Glass &

Pizzuto, 1994), or 33 ± 8 km (Prasad, Mahale, &

Kodagali, 2007). If un-melted ejecta estimates

are considered, which should provide an even

more accurate estimate, a 39 to 44 km (Glass,

2003) and 43 ± 9 km (Glass & Koeberl, 2006)

diameter crater estimate is derived. Studying the

compositional range of condensate droplets

(bottle-green microtektites), which reflect plume

cooling rate and therefore plume size, a 40 to 60

km diameter crater was estimated (Elkins-

Tanton, Kelly, Bico, & Bush, 2002).

Tektite distribution can be compared with

tektite / spherule strewn fields that have a

known crater, but source rock, fluid content, sea

depth, and impactor parameters, particularly

velocity and obliquity of impact may have

varied. It can be crudely ascertained that the

AAT source crater is likely larger than the 24

km diameter (Schmieder & Kring, 2020) Ries

Crater, significantly smaller than the 100 km

diameter (Schmieder & Kring, 2020) Popigai

Crater, and broadly comparable with the 40 to

45 km (Schmieder & Kring, 2020) Chesapeake

Bay Crater, with slumped outer rim of 80 to 90

km (Collins & Wünnemann, 2005).

In conclusion, a crater with 43 ± 9 km

diameter (Glass & Koeberl, 2006) should be

sought. If the crater is in a continental shelf

setting then, post-impact, it may be slumped to

80 to 90 km or more in diameter.

2.5 Obliquity of Impact / Crater Geometry:

The AAT impact was oblique, and this is very

adequately demonstrated by asymmetric morp-

hological and geochemical variations of tektites

that indicate the source crater is in the broad

Indochinese portion of the strewn field. The

obliquity of the impact would reduce the depth

and volume of melted and shocked materials at

the impact site and enhance the volume of ejected

melt (including tektites) (Pierazzo & Melosh,

2000). However, highly oblique impacts (<5°)

may have a negative effect on tektite production

as the first formed ejecta must travel a greater

distance to traverse the atmosphere.

To establish whether the impact was a highly

oblique (<5°) grazing impact, or an oblique (5°

to 30°) impact the distal ejecta pattern should be

reviewed. The AAT strewn field has a

downrange lobe of ejecta, mirroring forbidden

zones, and butterfly lobes, typical of impacts

below 45° (Gault & Wedekind, 1978). The

bilateral symmetry of the downrange ejecta is

broadly along a 164° azimuth and the butterfly

lobes are ~62° offset from the center of the

downrange ejecta. In grazing impacts that

produce elliptical craters a 90° offset from the

center of the downrange ejecta would be

anticipated (Gault & Wedekind, 1978).

Highly oblique grazing impacts result in

increased projectile contamination of the target

melt (Artemieva & Pierazzo, 2003; Stöffler,

Artemieva, & Pierazzo, 2002), something not

observed in AAT.

In a grazing impact there should be an uprange

forbidden zone, but in less oblique impacts the

uprange forbidden zone may close as the impact

Aubrey Whymark / Thai Geoscience Journal 2(2), 2021, p. 1-29 3

proceeds (Schultz, Anderson, & Hermalyn, 2009;

Schultz et al., 2007). Therefore, the presence of

uprange tektites is an argument against a grazing

impact. This will be discussed further as the

evidence is presented.

AAT distribution suggests an oblique impact

above 5° but, by comparison to Artemieva (2013),

under 30°. An oblique impact is optimal for melt

(tektite) ejection (Pierazzo & Melosh, 2000) and

will limit downward shock effects at the impact

site. The impact crater might be asymmetrical in

its depth profile, deeper in a north-northwesterly

direction, after Gault & Wedekind (1978). If there

was subsequent slumping this may be influenced

by the asymmetry of the post-impact crater profile

and might result in an elliptical slumped crater.

The above factors may result in a less pervasive

crater with atypical morphology. This would

make recognition more problematic.

2.6 Tektite Morphological Regression: AAT

fall into three transitional but readily differen-

tiable morphological groups, which can be

compared with tektites in strewn fields with a

known source crater. Distal tektites (e.g.,

Australites) were the first formed, highest velo-

city tektites. They underwent minimal plastic

deformation as the molten body exited the

atmosphere, suffered ablation during re-entry,

then spallation. Medial tektites (e.g., Philippi-

nites, Billitonites, and Bediasites) underwent

moderate plastic deformation as the molten body

exited the atmosphere, re-entry heating that was

insufficient for ablation to occur, and then

spallation. Proximal tektites (e.g., Indochinites,

Moldavites, Georgiaites, Ivory Coast Tektites)

underwent significant plastic deformation as they

interacted with the atmosphere at lower altitudes,

suffered minimal re-entry heating and minimal

spallation. Muong Nong-type (MN-type) layered

impact glass, whilst ballistically ejected, never

formed discrete surface tension-controlled

droplets due to lower melt temperature. MN-type

layered impact glasses represent the lowest

energy, theoretically most proximal, melts.

The lower ablation limit for tektites is about

5 km/s (Chapman, 1964). This is the defining

boundary between medial and distal tektite

morphologies. Within the AAT strewn field, the

most northerly ablated downrange tektites are

found in Sangiran, Java (Chapman, 1964). To

the north (along an azimuth towards Indochina),

tektites are not ablated and therefore re-entered

at velocities below about 5 km/s. Taking

Sangiran, Java, as the 5 km/s mark, and utilizing

trajectory calculations from Orbit 1.2 Software

(1998-2000), the crater likely lies somewhere

between 3,319 km away (37° ejection angle)

and 2,632 km away at 20° and 56.8° ejection

angle (shown in Fig. 1). At ejection angles lower

than 20° or higher than 56.8° (which are less

likely) the crater will be even closer. A potential

margin of error of hundreds (but not thousands)

of kilometers exists, but this calculation

indicates the most probable impact region and

rules out the wildest crater guesses where

modelled re-entry velocities do not match

observed physical attributes of the tektites. Re- -entry angles of tektites over Java were likely

quite oblique with angles of 20° to 25° probably

being realistic, implying a distance from the

source crater of 2,632 km to 2,992 km, again

within a margin of error being present.

Fig. 1: Taking Sangiran, Java, as the 5 km/s mark,

where the most northerly directly downrange ablated

tektites exist, the crater likely lies somewhere between

3,319 km away (37° ejection angle) and 2,632 km away

at 20° and 56.8° ejection angle. The AAT crater

probably lies within the belt highlighted in green. The

middle to southerly portion of the green shaded region

is most probable based on a 20° to 25° re-entry angle

for tektites in Java. The yellow area is lower

probability. Inset: Data used in map overlay. Green =

Probable regions; Yellow = Less favorable regions for

the AAT impact.


Increased target rock compressibility can

enhance melt production (Stöffler, Hamann, &

Metzler, 2018). Obliquity of impact can enhance

melt ejection (Pierazzo & Melosh, 2000). Water-

-rich surface layers can potentially enhance melt

production and ejection (K. T. Howard, 2011).

These factors, together with the size of the

impact, result in greater tektite abundance

(assuming suitable source rocks) and distance of

ejection (asymmetrically in the case of oblique

impact). Regardless of scaling, the distal, medial,

and proximal tektite morphological divisions

would be expected to be found at broadly the

same distance from the impact location. This is

because the morphological divisions are

primarily related to re-entry heating, controlled

principally by velocity. A re-entry tektite must

travel from the crater location to a fall location. It

can theoretically do so by any combination of

angle and velocity that achieves the defined

distance. Ejection angles of 15° to 50° result in

tektite velocities of: 2.87 to 3.74 km/s to land at

900 km; 3.70 to 4.50 km/s to land at 1,650 km;

and 6.40 to 7.05 km/s to land at 6,800 km from

the impact location (Orbit 1.2 Software, 1998- 2000). Velocity values are reasonably constrain-

ed regardless of the ejection angle.

Oblique impacts result in a low-angle

downrange ejection of the highest velocity melts

compared to vertical impacts that result in

higher angle omnidirectional ejection of melt

(Gault & Wedekind, 1978). The melt will travel

further in oblique impacts, but at lower angles.

In more energetic oblique impacts, sufficient

energy is present in the later stage of impact to

yield high-angle omnidirectional melts as well

as the initial higher velocity low-angle

downrange melt ejecta. So, at a set distance

from the impact crater the ejecta may be low-

-angle melts derived from a smaller oblique

crater or (low and) high-angle melts derived

from a larger oblique or vertical impact.

Morphological differences would be anticipated

between low- and high-angle melt ejecta. Low-

-angle tektites will encounter greater atmospheric

interaction. This manifests morphologically in

cascading to smaller bodies in a hot melt, or by

plastic deformation in a cooler more viscous melt

during exit, and in a longer duration of heating

during re-entry.

The question arises whether magnitude and

obliquity of impact, which may affect ejection

angle, influences the distance at which morpho-

logical groups theoretically occur. In short, it

does, but to a minimal degree: this methodology

will not offer precision but is expected to deliver

a broadly accurate result. This is because re-entry

velocity does not vary dramatically in response

to expected re-entry angles at a fixed location. It

is the tektite velocity that defines the boundary

between distal and medial forms. The medial to

proximal boundary is a little more complex:

again, the medial morphology requires a certain

re-entry velocity / heating, but spallation can be

over-ridden by the glass temperature in the re-

-entry phase. If the glass retained sufficient

temperature from formation, crack growth and

spallation are inhibited. Scaling may have greater

influence in the proximal realm, but the

prerequisite for sufficient velocity to produce

medial cores validates that all medial cores

should be found at similar distances from the

source. Variations in core morphology are

illustrated in Fig. 11 of Chapman (1964). Uncer-

tainty in comparisons may be reduced further by

comparing tektites from similar craters in terms

of magnitude, obliquity, and target.

The distance of proximal and medial North

American tektites from the Chesapeake Bay

source crater can be compared with Australasian

tektites. The two impacts are comparable in

terms of calculated magnitude and can be

inferred to have similar target rock characteristics

as both impacts yield widespread tektites. The

asymmetry of the North American tektite

distribution suggests the Chesapeake Bay impact

was oblique, although likely less oblique than the

AAT impact. Within the North American strewn

field, the medial tektite morphologies are found

at distances of 1,955 km to 2,180 km (O’Keefe,

1963) southwest from the point of impact. The

proximal North American tektites are found

predominantly to the southwest at distances of

635 km to 930 km (Povenmire, 2010; Povenmire

& Strange, 2006). The comparable Chesapeake

Bay impact is used to evaluate the AAT impact

crater location.

The Central European strewn field yields

proximal tektites at distances of 185 km to 430

km (Čada, Houzar, Hrazdil, & Skála, 2002; Trnka


& Houzar, 2002) from the Ries source crater.

The Ivory Coast strewn field yields tektites at

distances of 255 to 320 km (Gentner, 1966)

from the Bosumtwi source crater. These

smaller impacts demonstrate that true tektites

can occur in closer proximity to the crater.

The North American Bediasites are morpho-

logical equivalents to Philippinites, Malaysianites,

Brunei tektites, Billitonites and northern Indone-

sianites. In North America similar morphologies

occur at distances of 1,955 to 2,180 km (O’Keefe,

1963) from the impact site and do not occur within

930 km (Povenmire, 2010) from the impact site.

All locations within 930 km of medial tektite

occurrences can be eliminated as shown in red in

Fig. 2. It can be established that by 1,955 km there

are no proximal tektite morphologies (the true

number is likely much less but cannot be

calibrated). The source crater must be within

1,955 km of all proximal tektite morphologies.

This further restricts the potential source area

(green region in Fig. 2). A focal point can be

established by assuming all proximal tektites

occur within 930 km of the impact site. The actual

number is somewhere between 930 and 1,955 km

but likely close to the lower limit for the AAT

when cross referenced with other evidence

presented in this article. The focal point is

therefore an area of highest probability but does

not rule out surrounding areas. This approach is

demonstrated by the dark green region in Fig. 2.

2.7 Distribution of MN-Type Layered Impact

Glass: Muong Nong-type (MN-type) layered

impact glasses are the lowest temperature

ballistically (Huber, 2009; Koeberl, 1992;

Schnetzler, 1992) ejected melts. These impact

glasses are not entirely homogenized, are

volatile-rich in comparison to tektites, contain

relict mineral grains, and have alternating layers

of different composition (Koeberl, 1986).

Logically, MN-type tektites are expected to

occur in proximity to the source crater. A

triangular wedge-shaped ~65,000 km2 area was

noted in northeastern Thailand, southern Laos,

and central Vietnam where MN-type layered

impact glasses occur in the absence (or near-

-absence) of true splash-form tektites (Fiske et

al., 1999; Schnetzler & McHone, 1996) (see

Fig. 3). Further afield a mixture of MN-type

layered impact glasses and splash-form tektites

.

occur. Then further out, importantly in all

directions, only splash-form tektites, in the

absence of MN-type layered impact glasses,

occur (Fig. 3). This triangular wedge-shaped

area of MN-type layered impact glasses has

been assumed by many to represent the center

of the proximal tektite distribution and the

impact crater should lie close by. However, this

region of MN-type impact glasses is neither in

the most northwesterly part of the strewn field

nor in the center of the proximal splash-form

tektite and MN-type impact glass distribution:

instead, it is rather unsatisfactorily to the

southwest of center.

The triangular wedge of MN-type layered

impact glasses can be followed to the southwest

(see Fig. 3) and it appears to be the proximal part

of the prominent southwesterly butterfly ray.

Fig. 2: A map utilizing data from the North American strewn

field and comparing it with morphological groups of tektites

in the Australasian region. All medial tektites (e.g.,

Philippinites) should be at least 930 km from the source

crater, ruling out the areas in red. Medial tektite locations

used: 16.386186° N, 119.892056° E, Bolinao, Philippines;

10.955550° N, 119.405150° E, northern Palawan, Philip-

pines; 4.952386° N, 114.835486° E, Brunei; -2.923631° S,

108.206319°E, Belitung, Indonesia; 4.750000° N,

103.166667° E, Malay Peninsula, Malaysia. All proximal

tektites (e.g., Indochinites) should be within 1,955 km of the

source crater: possible areas are in green. If it is assumed that

all proximal tektites occur within 930 km of the source crater

(a number likely marginally too low) then the darker green

area is the most probable crater location (in reality, this is

almost certainly a broader area focused on this region as 930

km represents a minimum value). The yellow area is lower


Probable regions; Yellow = Less favorable regions; Red =

Incompatible regions for the AAT impact.


This ray extends into the central Indian Ocean

and beyond, almost reaching the southernmost

tip of Africa. The triangular wedge of MN-type

layered impact glasses points towards an origin

in the Gulf of Tonkin, possibly forming arcuate

rays in a cardioid (heart)-shaped pattern, with

reference to Schultz et al. (2009, 2007). A

mirroring wedge of MN-type layered impact

glasses would be expected on the southeasterly

butterfly ray that extends through northern

Manila and Paracale in the Philippines, onwards

in the direction of Micronesia in the southern

Pacific Ocean. This mirroring wedge of MN-

-type layered impact glasses cannot be

observed, if present, as it falls in the Gulf of

Tonkin and South China Sea. In support of its

presence, rare examples of MN-type layered

impact glasses have been found along the same

trajectory in Manila and Paracale in the Philip-

pines (Chapman & Scheiber, 1969; Whymark,

2020). It is apparent, as seen in all oblique crater

ray systems, that ejecta distribution is not equal.

This scenario is depicted in Fig. 3.

Regardless of whether the triangular wedge-

shaped area of MN-type layered tektites is

accepted as the center of distribution or whether

this region is accepted as the proximal part of the

southwesterly butterfly ray, with the

center of distribution in the Gulf of Tonkin, it

is evident the lowest temperature melts are not

concentrated in the most northwesterly area of

tektite distribution (i.e., Yunnan and Guangxi

regions of China and northern Vietnam) (Fig.4).

This observation is critical as it implies a

crater located in the center of the proximal part

of the strewn field and implies the presence of

uprange ejecta.

2.8 Tektite Crater Rays: Ejecta rays can be

seen emanating from craters on geologically

less active planetary bodies (e.g., the Moon,

Mercury, Ganymede). Increased gravity and

increased atmospheric density (e.g., Venus) will

act to suppress ejecta rays (Schultz, 1992). The

Earth has slightly greater gravity than Venus but

the atmosphere on Earth is significantly less

dense. Tektite droplets, forming from the ejecta

curtain at altitude, would be less inhibited on

Earth, compared with Venus. The presence of

distal AAT (e.g., Australites) that re-entered the

atmosphere (Chapman, 1964) is proof that AAT

ejecta was not wholly suppressed by the Earth’s

gravity and atmosphere. The distance that AAT

ejecta has travelled, by comparison to crater

rays on other planetary bodies, indicates that

tektites are part of a crater ray system as opposed

to randomly distributed.

In Australia, the prominent linear tektite

concentration that runs through South Australia,

Victoria, and into Tasmania has a distinct high

calcium (HCa) geochemical profile (Chapman,

1971). The combined linear tektite distribution and

distinct geochemistry indicate this feature is an

ejecta ray. The presence of at least one AAT ejecta

ray suggests the existence of a crater ray system.

Tektite distribution patterns, in terms of location,

abundance, and maximum tektite size, hint at a

further two ejecta rays in Western Australia. In the

Philippines, a prominent ray is suggested from

Zambales, through northern Manila, Rizal

Province (Tanay, Siniloan), Paracale, Catanduanes,

Fig. 3: The distribution of MN-type layered impact glas-

ses (green stars). The green region is predominantly MN-

type layered impact glasses in the absence (or near-

absence) of splash-form tektites (Fiske et al., 1999;

Schnetzler & McHone, 1996). This region has

traditionally been taken as the center of the Australasian

strewn field. In fact, it may represent one of two butterfly

rays emanating from the Gulf of Tonkin (suggested by

green dashed line) (Whymark, 2020). The most

prominent rays are indicated, with an assumed crater

position in the Gulf of Tonkin as per Whymark (2013)

(note that this location is not proven). Note how the green

region of MN-type layered impact glass and prominent

localities such as Muong Nong and Ubon Ratchathani lie

beneath this inferred ray. Inset: Data used in map

overlay. Green = Probable regions for the AAT impact.


and onwards into the Pacific Ocean. Notably,

this ray yields the largest splash-form tektites in

existence (Whymark, 2015). Further, less

distinct, rays may be present in the Philippines.

In the Malay Peninsula, an ejecta ray may be

present but is not sufficiently distinct to

confidently deduce an accurate azimuth.

Microtektite distribution has been widely

accepted to indicate two mirroring butterfly rays

(Glass & Koeberl, 2006; Prasad et al., 2007).

The southeast butterfly ray extends from the

northern Manila - Paracale region out into the

Pacific Ocean towards Nauru. The southwest

butterfly ray extends from the prominent Muong

Nong-type layered impact glass localities of

Muong Nong, Laos, and Ubon Ratchathani,

Thailand, into the Indian Ocean to a region

south of Madagascar.

Sufficient evidence exists from observation

(e.g., Chapman, 1971; Dunn, 1912; Fenner,

1935) and from modelling (e.g., Artemieva, 2013)

to indicate an uneven AAT distribution, in the

form of ejecta rays, in medial and distal tektites

and even possibly in the proximal setting (Izokh

& An, 1983). A non-random tektite distribution

implies that some tektite localities are related to

one another (by means of occurring at different

distances along the same ejecta ray). This

theoretically allows for a best-fit impact location

to be calculated. In doing so, stratigraphic

outcrop bias (minimal in the young AAT ejecta);

water transportation and redistribution (random-

ized on a global scale); the Coriolis effect (high

tektite velocities (Chapman, 1964) result in

minimal loft time); and post-impact plate

tectonics, must be considered. Since the AAT

impact, Australia is believed to have moved 54

km northwards with a slight clockwise rotation

(B. C. Howard, 2016). These values become

significant when regressing back thousands of

kilometers and lead to a significant easterly shift

in projections.

Fig. 4: Possible solutions for the distribution of MN-type layered impact glasses. Dark green stars represent

MN-type layered impact glass occurrence. Bright green stars represent splash-form or undifferentiated

tektite occurrence. Note how splash-form morphologies continue to occur at distance, surrounding the

centrally located MN-type layered impact glasses. The outer limit of the observed distribution on MN-type

layered impact glasses is shown by the dark green dashed line. The brown dashed line represents the

circular best fit. The absence of data to the east and southeast leaves a degree of uncertainty as to the center

of distribution. The presence of MN-type layered impact glass in the Philippines is suggestive that there is

another triangular wedge of MN-type layered impact glass along the southeasterly butterfly ray in the Gulf

of Tonkin and South China Sea. The triangular wedge of predominantly MN-type layered impact glass

(Fiske et al., 1999; Schnetzler & McHone, 1996) is likely the proximal part of the southwesterly butterfly

ray as opposed to the center of tektite distribution. This scenario is shown by the blue dashed line.

Regardless of the precise scenario, the center of distribution likely lies somewhere in the darker green

shaded region. The yellow area is lower probability. Inset: Data used in map overlay. Green = Probable

regions; Yellow = Less favorable regions for the AAT impact.


The use of a non-random tektite distribution

pattern, corrected for the Coriolis effect and

continental drift, should allow an accurate crater

position to be calculated. This is beyond the

scope of this article but is highlighted for future

research to provide additional layers of data.

2.9 Microtektite Regression: Microtektites are

found in the oceanic environment. Terrestrial

microtektites, other than those in salt lakes or ice,

are rapidly destroyed by dissolution in meteoric

waters. Microtektite regressions therefore utilize

a patchy distribution of distal oceanic borehole

locations. Numerous microtektite regression

studies have followed the same methodology but

have progressively used a greater number of

localities. The most recent study (Prasad et al.,

2007), utilizing the greatest number of localities,

is therefore the most accurate, superseding

previous studies (see Fig. 5, large ellipse). The R2

regression process was repeated using the same

methodology and data set from Prasad et al.

(2007), but with a higher density mesh (0.25°

spacing) to create a more detailed map and focal

region (Fig. 5, small ellipse).

Prasad et al. (2007) utilized 61 localities, of

which only 15 were from the easterly portion of

the strewn field and 46 from the westerly

portion. The distance from the approximated

source region also varied, with many easterly

localities being more proximal. Ultimately,

insufficient microtektite localities are available,

particularly on the northern (continental) and

eastern portion of the strewn field, to precisely

locate the crater. A notable observation is that

with increased microtektite localities the

regressed crater location has varied quite

considerably, and whilst becoming increasingly

refined, the focal point of regression still has the

possibility of readily shifting from its current

location with the addition of new microtektite

abundance data.

2.10 Target Lithology: Tektites, being a type of

natural glass, require a network former (primarily

silica), and therefore the source rock is

necessarily a silica-rich rock. If the impactor

strikes a silica-poor rock, then tektites cannot

form. Terrestrial weathering processes act to

concentrate silica in sedimentary rocks and their

metamorphic descendants. Tektites form through

shock melting so the temperature attained will be

dependent on the compressibility of the rock:

according to Stöffler, Hamann, & Metzler (2018)

“…at a given shock pressure, the shock

temperature of highly porous rocks can be up to

an order of magnitude higher than those of dense

crystalline rocks” (p. 2). Recently deposited

water-rich siliciclastic sediments, common on

the continental shelf, are therefore optimal for

tektite production (K. T. Howard, 2011). Older

siliciclastic sedimentary rocks are still suitable

but are denser at surface (due to previous burial

compaction) and so less compressible, followed

by metamorphosed siliciclastic sedimentary

rocks. Silica-rich igneous rocks, with low

compressibility, could still form tektites but a

much smaller volume of melt would attain

sufficient temperature to fully melt.

Clues as to the tektite source material can be

derived through the study of associated unmelted

and partially melted lithologies, mineral grains in

tektites and impact glasses (particularly in lower

temperature melts), and through analysis of the

geochemistry of fully melted tektites. Rock

fragments recovered from the Australasian

Fig. 5: An R2 microtektite regression map based on 61

localities from Prasad et al. (2007) (light green).

Utilizing identical methodology and dataset, but with a

higher density of regression points, a focal point was

calculated (dark green). The impact crater likely lies

within the green region, with the darkest green region

being most probable. The yellow area is lower


Probable regions; Yellow = Less favorable regions for

the AAT impact.


microtektite layer were found to be well sorted,

quartz-rich, fine-grained (silt- to fine sand-sized)

sedimentary rock (Glass & Barlow, 1979; Glass &

Koeberl, 2006). A derivation from shales,

graywackes, and lithic arenites has been suggested

(Glass, Huber, & Koeberl, 2004; Koeberl, 1992).

In agreement, K. T. Howard (2011) suggested a

mixture of shale-like material and a very quartz-

rich material. A minor carbonate (dolomite)

component was suggested to explain the CaO

(positively correlated with MgO) variation

(Amare & Koeberl, 2006).

Coarse-grained sedimentary rocks such as

sandstones and conglomerates, as have been

commonly described from Jurassic sediments in

the central Indochinese region (Blum et al., 1992;

Javanaphet, 1969; Sieh et al., 2020) (Fig. 6), are

unsuitable source materials for AAT despite

theoretically being suitable for tektite formation.

This is further confirmed by REE analyses.

Interlayered silts and shales may be suitable

source materials, but not when considered in this

heterogeneous context.

Based on principal component analysis

(PCA) using major-element tektite composition

an admixture of sandstone and basalt was

proposed by Sieh et al. (2020). As discussed in

Section 2.15, thorough mixing is demonstrably

poor in tektites (Glass & Simonson, 2013, p. 113;

Koeberl, 1992). AAT REE data is incompatible

with sandstone (Fig. 7) and basalt sources (Fig. 8)

(Koeberl, 1992). Sr-Nd isotopic data is incom-

patible with basalts (N. Hoang, Flower, &

Carlson, 1996; N. Hoang, Hauzenberger, Fuku-

yama, & Konzett, 2018). PCA did, however,

highlight compositional variations between early

(distal) and late (proximal) formed tektites,

reinforcing trends also seen in REE and Sr-Nd

isotopes, indicative of a lithological variation

with depth of excavation if a ballistic equivalent

of ‘inverted’ stratigraphy is accepted. Igneous

rocks as a target material are highly improbable

from a geochemical (presented subsequently)

and wide AAT distribution perspective. Impact-

-related melts should not be surface exposed in a

recent impact that has suffered minimal erosion.

Igneous provinces are improbable source regions

(Fig. 6).

2.11 Rare-Earth Elements: Koeberl et al.

(1985) states that rare-earth elements (REE) are

known to be of “great genetic significance”

(p. 108). REE are refractory elements, and their

abundance pattern has not changed in the process

of melting (Koeberl et al., 1985). Chondrite

(McDonough & Sun, 1995) normalized REE

patterns of averaged tektite values can be

compared with various rock types. Koeberl et al.

(1985) concluded that AAT ‘…follow very

closely the pattern exhibited by the post-Archean

upper crust average sediments and are very likely

to have originated from such a source’ p. 107.

Averaged shale groupings (Condie, 1993;

Howard, 2011; Koeberl et al., 1985; Lodders &

Fegley, 1998), see Fig. 7, were highly comparable

with AAT values. Graywacke values (Condie,

1993; Koeberl et al., 1985), see Fig. 7, conformed

to the later stage splash-form and layered tektites.

Sandstones (Condie, 1993; Koeberl et al., 1985),

see Fig. 7, had low REE values, incompatible as a

sole source for AAT.

Fig. 6: A geological map outlining potentially suitable and

unsuitable rock types for AAT. Mesozoic rocks (lime

green), including Middle Jurassic strata. Quaternary

outcrops and continental shelf areas (dull sea-green) which

likely yield recent sediments. Green regions yield rocks of

potentially suitable ages (dependent on various Rb/Sr and 10Be interpretations) and may be compatible with the site

of impact. Intrusive igneous rocks (bright yellow) are

unlikely source materials and impact melts should not be

surface exposed. Extrusive volcanic rocks (beige) are

unlikely source regions due to geochemical

incompatibility. Dull yellow regions represent outcropping

rocks of incompatible age and incompatible deeper sea

sediments. Yellow / beige regions have a low compatibility

with the site of impact. After Liu et al. (2016). Inset: Data

used in map overlay. Green = Probable regions; Yellow =

Less favorable regions for the AAT impact.


Fig. 7: Chondrite (McDonough & Sun, 1995) normalized rare-earth element patterns of average tektite values [a] (K.

T. Howard, 2011) compared with shale, graywacke, and sandstone values. [a] K. T. Howard (2011) after Lodders &

Fegley (1998); [c] Koeberl et al. (1985); [d] Condie (1993).


T. Howard, 2011) compared with Meso-Cenozoic basalt values: [d] Condie (1993). Various plotted Bolaven basalt

compositions are duplicated from [e] N. Hoang et al. (2018).



T. Howard, 2011) compared with Upper Miocene sediment values: [b] (Cao et al., 2015). Bright green wells were

categorized by (Cao et al., 2015) as Group 1 wells with relatively high REE concentrations. Dark green wells were

categorized by (Cao et al., 2015) as Group 2 wells with relatively low REE concentrations. Pale green wells were

uncategorized, falling into both Group 1 and 2 with some anomalies.

REE values for basalt (including Bolaven

Plateau basalts), see Fig. 8, did not reproduce the

AAT REE pattern (Condie, 1993; N. Hoang et al.,

2018). Basic igneous rocks can be excluded as a

potential source material for AAT (wholly or in

part) based on REE (N. Hoang et al., 1996, 2018;

Koeberl, 1992) (Fig. 8). Koeberl (1992) states:

‘Mixing of local soils, or with some related

loess samples, cannot reproduce the tektite

REE patterns, and any basaltic, oceanic, or

extraterrestrial rocks can be excluded as source

rocks…’ p. 1033. Figs. 7 & 8 demonstrate that

REE patterns of sandstones and basalts, either

in isolation or in combination, are incompatible

with AAT.

All shales have similar REE patterns, so it is

not possible to determine the exact precursor rock /

formation from which AAT originated (Koeberl

et al., 1985). It can simply be determined that the

source rock was shale-rich and post-Archean

(Koeberl et al., 1985). Averaged tektite values

from K. T. Howard (2011), suggest that earlier

formed microtektites have, on average, higher

REE concentrations than splash-form tektites,

which in turn have higher REE concentrations

than the last formed layered ‘tektites’ (Figs. 7 - 9).

If a ballistic equivalent of ‘inverted’ stratigraphy,

a concept that is not proven but appears likely, is

accepted then REE may indicate a subtle transi-

tion from shales to siltier / sandier interbedded

shales or graywackes with greater depth of

excavation.

Australasian tektite REE values can be

compared with Upper Miocene sediments from

boreholes in the Yinggehai Basin and Qiong-

dongnan Basin (Cao, Jiang, Wang, Zhang, &

Sun, 2015), see Fig. 9. AAT REE values were

comparable with sediments containing high

REE concentrations, categorized as Group 1 wells

by Cao et al. (2015). Average AAT microtektite

values closely matched well LT33. Average

AAT splash-form and layered ‘tektite’ values

were comparable with wells HK17 and LT1, see

Fig. 9. In the sparse data set, in terms of

geographic and stratigraphic extent, Group 1

wells corresponded with regions surrounding


Hainan, but notably no data for comparison is

available offshore Vietnam. Sediments close to

the Red River mouth and in central Qiongdongnan

Basin showed low compatibility (Figs. 9 & 10).

Cao et al. (2015) did not compare lithology to

REE abundance. It is possible that compatible

wells simply represent shale-rich sediments.

Incompatible wells may represent sand-rich

submarine or deltaic fans derived from rivers

(Fig. 10). The most prominent river is the Red

River which progrades into the northern part the

Yinggehai - Song Hong (YGH-SH) Basin.

Tektite REE data appears to preclude coarser

siliciclastic sediment and, as such, may

indicate a crater position away from a river

mouth and its extended submarine fans.

2.12 Strontium - Neodymium: Sr-Nd isotopic

data can potentially be used to ‘fingerprint’ the

source rock. As highlighted in Section 2.15,

thorough mixing is demonstrably poor in

tektites (Glass & Simonson, 2013, p. 113;

Koeberl, 1992). The close grouping of Sr-Nd

values in tektites (Fig. 11) would therefore be

suggestive of a relatively homogenous target

rock as opposed to thorough and efficient

mixing of disparate melts (e.g., basalt and

sandstone) in the brief seconds following

impact. The constituents of fine-grained

sedimentary rocks, identified as the probable

source material (Section 2.10), are thoroughly

mixed and homogenized by sedimentary

transport processes resulting in consistency if

derived from the same parent materials. Fig. 11

demonstrates reasonably homogenized sedi-

ments in basins, versus the diversity in

immature river sediments. In the suggested

absence of thorough mixing of tektite melts a

relatively homogenous source rock is

interpreted.

Cross plots of 87Sr/86Sr against εNd values

were constructed to compare published AAT

values (Ackerman et al., 2020; Blum et al., 1992;

Shaw & Wasserburg, 1982) with published river

sediment data (Clift et al., 2008; Jonell et al.,

2017; Liu et al., 2007) and with surface

sediments of the South China Sea region (Wei et

al., 2012), see Fig. 11. Slight differences in 87Sr/86Sr and εNd values between proximal and

distal tektites are potentially indicative of

derivation of tektites from variable depths in a

stratified, but generically related, target (Blum et

al., 1992). These data indicated a compatibility of

AAT with sediments at the Red River mouth and

the East Vietnam and South China Seas (see

Figs. 11 & 12). Samples were not available in the

Yinggehai - Song Hong (YGH-SH) Basin but

modern-day Red River drainage accounts for

approximately 80% the total sediment supply of

the YGH-SH Basin (Feng et al., 2018). When

sediment supply exceeded accommodation space

in the YGH-SH Basin, the sediment ‘spilled’ into

the East Vietnam and South China Seas. By

inference, a YGH-SH Basin source, located

between compatible sources and sinks, is likely

compatible.

Australasian tektite samples yielded εNd

values between -10.9 and -12.2, averaging -11.58

(Ackerman et al., 2020; Blum et al., 1992; Shaw

& Wasserburg, 1982). These consistent εNd

values are indicative of a reasonably homo-

genous target material, or improbable scenario of

a thoroughly mixed melt, from a single source

crater. εNd values from the Red River mouth were

-11.47 (Liu et al., 2007, 2016). AAT εNd values

conformed closely with εNd values from the Red

Fig. 10: REE compatibility of Upper Miocene sediments

(Cao et al., 2015) with AAT (K. T. Howard, 2011). Wells

with compatible Upper Miocene sediment are marked

with a green circle and shaded green. Incompatible wells,

likely representing sandier deposits, are marked with a

red cross and shaded yellow. Stratigraphically results

will vary. No data from Vietnamese wells. Modern rivers

are depicted in blue, which are anticipated to deliver

sand-rich sediments. Inset: Data used in map overlay.

Green = Probable regions; Yellow = Less favorable

regions for the AAT impact.


River mouth, YGH-SH Basin, Qiongdongnan

Basin, Pearl River mouth and west Zhujiangkou

Basin (fed by the Pearl River with Hainan

influence). εNd values used to construct a map of

potential source areas (see Fig. 13).

Sr-Nd isotopic data of southern Vietnamese

Basalts (N. Hoang et al., 1996) can be compared

with tektites (Ackerman et al., 2020; Blum et al.,

1992; Shaw & Wasserburg, 1982). In southern

Vietnamese basalts 87Sr/86Sr values average

0.744 (0.7036 to 0.7065), compared to AAT that

average 0.7169 (0.7118 to 0.7213); 143Nd/144Nd

values average 0.5128 (0.5126 to 0.5130),

compared to AAT that average 0.5117 (0.5112

to 0.5121); εNd averages 3.72 (-0.9 to 7.6),

compared to AAT that average -11.58

(-12.2 to -10.9) (Ackerman et al., 2020; Blum et

al., 1992; N. Hoang et al., 1996; Shaw &

Wasserburg, 1982). Values for Bolaven are not

given, but 87Sr/86Sr and 143Nd/144Nd values of

Bolaven basalts are plotted in N. Hoang et al.

(2018) and fall centrally within the ranges of

southern Vietnamese basalt values of N. Hoang

et al. (1996). It is demonstrated that regional

Fig. 11: Cross plot of Sr versus Nd isotope com-

positions of Australasian tektites and potential source

materials from river basins and offshore basins. AAT

overlap with Red River sediments, offshore Indochina,

the Northwest Basin, and the Southwest Basin. No data

was available for the YGH-SH Basin.

Fig. 12: Location of samples in cross plot (see Fig. 11)

of Sr versus Nd isotope compositions for tektites

(Ackerman et al., 2020; Blum et al., 1992; Shaw &

Wasserburg, 1982) compared with basin sediments

measured from offshore Hainan, Beibuwan Bay,

offshore Indochina, Northwest Basin and Southwest

Basin (Wei et al., 2012) and river sediments (Clift et al.,

2008; Jonell et al., 2017; Liu et al., 2007). Samples with

a star and green shaded areas are closely compatible

with tektites. Samples denoted by a circle and yellow

shaded areas indicate low compatibility with AAT.

Modern rivers are depicted in blue. Inset: Data used in

map overlay. Green = Probable regions; Yellow = Less

favorable regions for the AAT impact.

Fig. 13: Modern εNd values from (Liu et al., 2016).

These values can be compared with tektite samples

that yielded εNd values between -10.9 and -12.2,

averaging -11.58 (Ackerman et al., 2020; Blum et al.,

1992; Shaw & Wasserburg, 1982). Green areas

represent suitable source areas. Yellow areas

represent unlikely source areas. Inset: Data used in

map overlay. Green = Probable regions; Yellow =



basalts are incompatible as a source material for

AAT.

2.13 Major Element Geochemical Regression:

The geographic distribution of SiO2, Na2O, and

CaO concentrations in MN-type layered

impact glasses and intermediate tektites are

plotted from Schnetzler (1992) (Figs. 14 - 16).

Schnetzler (1992) utilized a sparse data set with

some approximated or poorly defined localities

(SiO2 = 22 localities / 166 analyses; Na2O = 23

localities / 97 analyses; CaO = 24 localities / 98

analyses). The absence of data from the Gulf of

Tonkin, East Vietnam Sea, and South China

Sea potentially skews data westwards. Whilst

trends are observed, the contours are somewhat

subjective, and the possibility of erroneous

localities cannot be dismissed. The use in map

overlay, however, remains valid as the principle

combines weak data to create a more robust

argument through weight of evidence. The major

element geochemical iso-concentrations in

Schnetzler (1992) appear to trend to the center of

the proximal tektite strewn field.

2.14 Beryllium-10 Regression: A trend of

decreasing 10Be content with proximity to the

likely source area is observed (Table 1). This

trend in 10Be iso-concentrations within the AAT

strewn field is increasingly being accepted as

representing a ballistic equivalent of ‘inverted’

stratigraphy (Ma et al., 2004). An ‘inverted’

stratigraphy should be more evident if a thick

sedimentary column has been sampled. 10Be

iso-concentrations of MN-type layered impact

glasses were used by Ma et al. (2004) to

calculate the crater position with the assumption

that the crater would lie at the center of the

lowest concentration of 10Be (Fig. 17).

2.15 Target Lithology Age: Rb-Sr versus 10Be:

There is conflicting data regarding the strati-

graphic age of the target material. Resolving

this issue would significantly narrow down the

crater search area. The conflicting data are:

• It was determined that the last major Rb-Sr

fractionation event (i.e., weathering, trans-

portation, and deposition) experienced by the

sedimentary target materials occurred in a

narrow range of stratigraphic ages ~170 Ma

ago (Blum et al., 1992).

• The 10Be content in tektites, half-life of 1.39

Ma (Chmeleff, Blanckenburg, Kossert, &

Jakob, 2010; Korschinek et al., 2010), was

recognized as being too high to be derived

from a Middle Jurassic source rock (Blum et

al., 1992). It was concluded by Ma et al.

(2004) that the AAT source material “did

not consist of older igneous or sedimentary

rocks, but of unconsolidated materials or

young sedimentary rocks” (p. 3887).

There are three solutions that might theoretically

provide satisfactory outcomes (Fig. 18):

1) There is thorough mixing between

Middle Jurassic rocks and a young

surficial cover during melt production. If

it were a young fluvial sediment cover a

~1:4 ratio of young fluvial sediment to

Middle Jurassic rock (Blum et al., 1992)

would be expected.

2) The source rock is solely Middle Jurassic

in age. A weathered surface in the target

area was exposed to meteoric waters for

longer than the half-life of 10Be and if 10Be was not lost to erosion or solution

then a ~200 m column of Middle Jurassic

bedrock could yield the correct 10Be

content (Blum et al., 1992).

3) The source rock is a young unconsolidated

sedimentary rock (Ma et al., 2004). This

suggests that the Rb-Sr clock may not have

been reset and represents the penultimate

depositional cycle (at ~170 Ma) or an

averaged Rb-Sr age (Cordani, Mizusaki,

Kawashita, & Thomaz-Filho, 2004; Dic-

kin, 2005).

Mixing is demonstrably poor in microtektites

according to Glass & Simonson (2013): “There

is not time for impact melt to be thoroughly

mixed and homogenized prior to being ejected”

(p. 113). Koeberl (1992) states that the lower

temperature, MN-type layered impact glasses

are “…compatible with incomplete mixtures of

different target rocks” (p. 1056). It is assumed

that microtektites represent early stage,

typically shallow derived, melts whereas MN-

-type layered impact glasses represent later stage,

on average more deeply excavated, melts. The

compositional layering in MN-type impact glasses


Fig. 16: The geographic distribution of CaO con-

centrations in MN-type layered impact glasses and

intermediate tektites based on 24 localities / 98

analyses (Schnetzler, 1992). Note the absence of

data to the east and southeast due to the presence

of seas. Green regions represent regions of higher

probability and yellow areas denote lower

probability for the presence of the AAT source

crater. Inset: Data used in map overlay. Green =

Probable regions; Yellow = Less favorable regions

for the AAT impact.

Fig. 17: Regression of 10Be iso-concentrations (Ma

et al., 2004) indicate the crater is within the shaded

region, with the best fit at ‘•’. Note the absence of

data to the east and southeast due to the presence of

seas. The yellow shaded area denotes lower

probability for the AAT source crater. Inset: Data

used in map overlay. Green = Probable regions;

Yellow = Less favorable regions for the AAT

impact.

Fig. 15: The geographic distribution of Na2O con-

centrations in MN-type layered impact glasses and


analyses (Schnetzler, 1992). Note the absence of data

to the east and southeast due to the presence of seas.

Green regions represent regions of higher probability

and yellow areas denote lower probability for the

presence of the AAT source crater. Inset: Data used

in map overlay. Green = Probable regions; Yellow =


Fig. 14: The geographic distribution of SiO2 concen-

trations in MN-type layered impact glasses and


analyses (Schnetzler, 1992). Note the absence of data

to the east and southeast due to the presence of seas.

Green regions represent regions of higher probability

and yellow areas denote lower probability for the

presence of the AAT source crater. Inset: Data used in

map overlay. Green = Probable regions; Yellow =



Table 1: Average 10Be concentrations of tektites grouped by country. Sources: [1] = (Ma et al., 2004); [2]

= (Rochette et al., 2018); [3] = (Koeberl, Nishiizumi, Caffee, & Glass, 2015). Note that corrections for in

situ 10Be production are minimal, not exceeding ~10 × 106 atom/g (Ma et al., 2004, after others).

Country Average 10Be (atoms/g) Source

Laos 59 ±9 × 106 (uncorrected) [1]

Thailand 71 ±17 × 106 (uncorrected) [1]

Vietnam 73 ±13 × 106 (uncorrected) [1]

China 85 ±24 × 106 (uncorrected) [1]

Indonesia 115 ±27 × 106 (uncorrected) [1]

Philippines 121 ±22 × 106 (uncorrected) [1]

Australia 136 ±30 × 106 (uncorrected) [1]

Microtektites:

Antarctica 184 ±8 × 106 (corrected

for in situ production)

[2]

S. China Sea 260 ±60 ×106 [3]

Fig. 18: Three scenarios that satisfactorily explain the Rb-

Sr and 10Be values.

may reflect sedimentary bedding, indicative of

melting with practically no mixing, implying 10Be content at depth. It was remarked by Ma et

al. (2004): “assuming that during crater

formation neither the precursor grains nor the

material melted mixed efficiently on a scale of

tens of meters (N. A. Artemieva and E. Pierazzo,

personal communication, 2002) we conclude

that the vertical extent or thickness (as opposed

to the absolute depth) of the hypothetical region

that participated in tektite formation was likely

between 15 and 300 m.” (p. 3892).

The assumption made in Ma et al. (2004) was

that if mixing is poor then high 10Be values in

tektite demonstrate a surficial origin (15 to 300 m).

This has been supported by numerous authors:

~200 m (Blum et al., 1992); X0 m (Trnka, 2020);

first tens of cm’s of soil / sediment for Antarctica

microtektites (Rochette et al., 2018). This

assumption, however, is incorrect as it assumes

an impact on land or in a region of normal

sedimentation. Within the region of most

probable impact (i.e., Indochinese to southern

Chinese region) the YGH-SH Basin in the Gulf

of Tonkin demonstrates exceptionally high

sedimentation rates and therefore presumable

abnormally high 10Be content at great depth.

Sediments predominantly comprise siliciclastic

continental material in a deltaic to shallow

marine setting. High 10Be values in AAT do not

demonstrate a surficial origin unless the source

crater geology is known. 10Be content does,

however, potentially allow a crude understanding

of stratigraphy at the unknown impact location if

depth of excavation of tektites can be

independently estimated.

Artemieva (2008) states that: “Excavation

depth (initial position of ejecta in the target)

drops quickly with increasing ejection velocity:

from 0.25 Dpr for 2 km/s to 0.02 Dpr for 11

km/s” (p. 1) (Dpr = diameter of projectile). The

trajectories of tektites, neglecting atmospheric

drag, were calculated (Schmitt, 2004): at 2 km/s

material is ejected laterally 204 km at 15º and

75º; 312 km at 25º and 65º to a maximum of 408

km at 45º. Moldavites, from Ries Crater, occur

at distances beyond ~185 km. Assuming

ejection angles from 15º to 75º, neglecting

atmospheric drag, corresponding velocities of

1.35 to 1.9 km/s are calculated for these

Moldavites, suggestive that tektites are present

in ejecta travelling at under (or certainly close

to) 2 km/s.


Atmospheric drag will, to varying degrees,

raise the launch velocities required to eject a

body a certain distance, in turn reducing the

depth from which tektite could have been

produced. In the early stages of impact, material

is jetted (Vickery, 1993) and discrete tektite

droplets form from the ejecta curtain at variable

altitudes. The rarefied atmosphere is demon-

-strated by tektite bubble pressures (Matsuda,

Maruoka, Pinti, & Koeberl, 1996; Mizote,

Matsumoto, Matsuda, & Koeberl, 2003;

Zähringer & Gentner, 1963). In larger impacts,

such as the AAT impact, the influence of

atmospheric drag is less prominent as the ejecta

accelerates the atmosphere (Shuvalov &

Dypvik, 2013). The large size of the AAT

impact and the evidence of the formation of

discrete tektite droplets at altitude significantly

reduces, but does not eliminate atmospheric

interaction, as manifested in the plastic

deformation of tektite droplets, especially in

proximal morphologies.

It is reasonable to assume that the AAT

impact was comparable in size to the Chesapeake

Bay impact (or possibly marginally larger),

which is believed to have been produced by a 3.2

km diameter impactor (Kenkmann et al., 2009).

An impactor of this diameter might excavate

tektite producing ejecta to a depth of 800+ m,

after Artemieva (2008), assuming no / shallow

seas and suitable glass-forming lithologies in the

stratigraphy. Three possible impact scenarios can

now be presented:

A) The impact was a highly oblique grazing

impact (< 5º) resulting in an elliptical

crater. Consequently, tektites were only

produced from surficial material.

B) The impact was oblique and resulted in a

near-circular crater. However, tektites

were only produced from the surficial

layers as the strata at depth was incom-

patible with glass formation (e.g., lime-

stone or anhydrite).

C) The impact was oblique and resulted in a

near-circular crater. Tektites were pro-

duced from rock derived from the surface

to ~800 m depth.

The arguments can be readily tested as the

surficial (early stage) origin of tektites (A & B)

necessitate that ejecta is predominantly

downrange with a distinct uprange zone of

avoidance (Gault & Wedekind, 1978; Schultz et

al., 2009, 2007), i.e., an impact in northernmost

Vietnam or Yunnan Province in China. Whereas

C would eject tektites throughout the 360º

azimuthal range (uprange and downrange) (Gault

& Wedekind, 1978) with a crater in the center of

the proximal strewn field (Ubon Ratchathani

Province of Thailand, Savannakhét, Salavan, and

Champasak Provinces of central-southern Laos,

central Vietnam, and the Gulf of Tonkin).

Scenario A has been discussed and can be

dismissed based on the azimuth of the butterfly

lobes (Gault & Wedekind, 1978). Multiple

parameters, including microtektite regression

(Prasad et al., 2007), geochemical regression

(Ma et al., 2004; Schnetzler, 1992), and MN-

-type layered impact glass distribution (Schnet-

zler, 1992) all point to a broadly central crater

position either in the central-eastern part of

Indochina or into the Gulf of Tonkin. This

dictates that the proximal ejecta in this oblique

impact is, in part, uprange and was therefore

later stage, coming from depth as the circular

crater opened-up. The observations of uprange

AAT indicate the solution is Scenario C. Whilst

tektites are typically considered downrange

ejecta, it is notable that the Chesapeake Bay

Crater produced rare probable uprange ejecta at

Martha’s Vineyard (Burns, Schnetzler, &

Chase, 1961).

Poorly mixed MN-type layered impact

glasses are therefore assumed to be derived

from up to ~800 m depth, after (Artemieva,

2008). The implication of high 10Be values at

depth in the presence of poor mixing, is that

there is a thick sequence of recent sediments at

the impact site. Some ballpark calculations for

the impact site stratigraphy can be made if the 10Be iso-concentrations are interpreted to

represent a ballistic equivalent of ‘inverted’

stratigraphy. Assuming the impact was pene-

contemporaneous with sediment deposition,

Antarctic, and South China Sea microtektites

represent the first formed surficial ejecta, and

tektites in Laos represent the last formed ejecta,


a 2.28 to 2.97 Ma packet of sediment was

sampled by AAT (early Pleistocene to Pliocene).

Assuming ~800 m depth was sampled; an

average sedimentation rate of 269 to 351 m/Ma

is derived. The calculations are crude owing to

multiple variables, but the principal point is that

acceptance of uprange tektite distribution

demonstrates excavation from depth and by

inference a thick sequence of recent, rapidly

deposited, sediment was sampled by AAT.

Even if the sediment column estimate was

reduced in consideration of atmospheric drag,

the same conclusions will apply. Material is not

ejected uprange until later stages of impact as

the circular crater forms.

To reset the Rb-Sr clock substantial

exchange and homogenization of Sr with sea /

formation water is required. Rapidly deposited

sediments, especially in a deltaic, but even in

open marine environments, may preserve

previous Rb-Sr dates (Cordani et al., 2004) / an

average of the provenance ages of the sedimen-

tary constituents (Dickin, 2005).

A very fine, almost authigenic, claystone

comprising minerals such as illite, free from

detrital minerals, is optimal to reset the Rb-Sr

clock (Dickin, 2005). A low percentage of illite

might be taken as an indicator that the region is

unsuitable for resetting the Rb-Sr clock, and as

such may indicate viability as a source crater

region (Fig. 19). In the YGH-SH Basin, clay

mineral transformation, including illitization,

typically occurs below 2,000 m sediment depth

(Jiang, Xie, Chen, Wang, & Li, 2015). The

uppermost 2,000 m of YGH-SH Basin

sediment (deposited shortly before the impact

and melted and ejected prior to illitization)

would fulfil the 10Be and Rb-Sr observations.

2.16 Pore Water / Sea Water Mixing

Considerations: Tektites have very low water

contents (Beran & Koeberl, 1997) due to the

high formation temperatures that cause water

to dissociate into H+ and O2- ions (Vickery &

Browning, 1991). Ackerman, Skála, Křížová,

Žák, & Magna (2019) believe that “volatile

species derived from dissociated seawater and/or

saline pore water” (p. 179) may aid the loss of Os

in the form of Os oxides. According to

Ackerman et al. (2019) “The low Os abundance

in most of the analyzed Australasian tektites,

combined with non-radiogenic 187Os/188Os far

below average upper continental crust, may

provide a direct test to distinguish continental

versus seawater impact scenario” (p. 179). The

presence of significant amounts of water is

envisaged in the formation of AAT (Ackerman

et al., 2019). This work followed K. T. Howard

(2011) who had noted that where tektites are

present, a water-rich surface layer can be

inferred. The abundance and widespread

distribution of AAT necessarily implicates a

water-rich target.

A saline character of the pore water is

supported by the elevated halogen content of

AAT (Ackerman et al., 2019; Koeberl, 1992;

Meisel, Langenauer, & Krähenbühl, 1992). AAT

were noted to have relatively high B and Li

abundances and 𝛿11B values of (-4.9 to +1.4‰)

(Chaussidon & Koeberl, 1995). The B, Li, and

𝛿11B values were indicative of a source rock with

a higher clay content and are consistent with

marine pelagic and neritic sediments as well as

river and deltaic sediments (Chaussidon &

Koeberl, 1995). 10Be, Rb-Sr and Sm-Nd values

Fig. 19: Illite percentages in modern sediments after Liu

et al. (2016). Solid lines with darker green shading

represent under 20% illite. Dashed lines with lighter

green shading represent under 30% illite. Yellow shaded

regions yielded over 30% illite and represent lower

probability regions. The Gulf of Tonkin region averages

27% illite. If it is assumed that the Rb-Sr clock was not

reset, then areas of low illite concentrations represent

plausible impact locations as these are the least suitable

clay-rich rocks for obtaining a reset Rb-Sr age. Inset:

Data used in map overlay. Green = Probable regions;

Yellow = Less favorable regions for the AAT impact.


were indicative of a continental crustal source

rock (Blum et al., 1992) and eliminated pelagic

and deeper neritic sediments (Chaussidon &

Koeberl, 1995). It was concluded that AAT were

derived from river and deltaic sediments with a

higher clay content that have acquired B from the

seawater (Chaussidon & Koeberl, 1995).

Offshore Mekong River delta sediment was

considered a potential source due to the rapid

deposition rate of 10Be-rich sediments (Chau-

ssidon & Koeberl, 1995). A Mekong River

source can now be eliminated by poorly

compatible εNd values (Liu et al., 2007) and

geographic position. The same conclusions,

however, exceedingly accurately fit a Red River

derived YGH-SH Basin source.

2.17 Sea Level in Source Region: The AAT

impact occurred immediately prior to Termi-

nation IX, the transition from Marine Isotope

Stage 19-20 (Mark et al., 2017). So, the impact

occurred during a glacial stage when sea levels

were low. Continental shelf regions, including

the Gulf of Tonkin, would have been subaerially

exposed, deltaic, or shallow shelf seas.

It is suggested that water-rich surface layers

enhance, by orders of magnitude, the production

of high velocity ejected melt (K. T. Howard,

2011). Recently deposited, uncompacted, silici-

clastic sediments have a much higher pore water

content compared to mature sedimentary rocks

exposed at the surface and are therefore optimal

for tektite production.

It was modelled that an impact into 300 m

water depth, compared to dry land, will result in

a greater distribution of tektites (Artemieva,

2013). A 300 m water depth, however, would

significantly curtail the production of the highest

velocity distal ejecta, by reference to Artemieva

(2008), which are notably present in abundance.

With greater water depth the lithologies become

geochemically (10Be, Rb-Sr) less suitable. A

water depth of tens of meters (or less) correspond-

ing to a glacial lowstand on the continental shelf

is likely to be realistic (Fig. 20). The source

region might be broadly envisaged within the

realm of a river delta to shallow shelf sea

containing poorly compacted, rapidly deposited

sediments with saline pore waters.

Fig. 20: The deeper seas in red cannot be considered as

potential source areas as they could not produce the

distal tektites. The areas in green are continental shelf

regions (to 500 m below present sea level) (Liu et al.,

2016). This shelf region is ideal for tektite production

and some of this area would have been land during

glacial lowstand. The area in yellow represents land

areas which have a low probability of yielding the AAT

source crater, simply because the crater would be evident

and could not have been buried or eroded. Inset: Data

used in map overlay. Green = Probable regions; Yellow

= Less favorable regions; Red = Incompatible regions

for the AAT impact.

2.18 Absence of Tsunamis Deposits: An impact

on land or in a shallow sea would not be expected

to produce significant tsunamis: resultant

tsunamis would potentially be undifferentiable,

in terms of magnitude, from tectonic tsunamis.

Given the lower sea levels at the time of impact

any evidence of tsunamis is likely below the

current sea level.

2.19 Evidence of Cataclysmic Deposits: In

northeastern Thailand tektite-bearing flood

deposits have been reported from Ban Ta Chang

(15.037° N, 102.291° E) and Chum Phuang

(15.381° N, 102.728° E) (Bunopas et al., 1999).

The presence of tektites and reversed polarities

constrains the sediment to a period between the

AAT impact event = 786 ± 2 ka (Mark et al.,

2017) and the Brunhes / Matuyama polarity

reversal = 783.4 ± 0.6 ka (Mark et al., 2017)

(Haines, K. T. Howard, Ali, Burrett, &

Bunopas, 2004; K. T. Howard, Haines, Burrett,

Ali, & Bunopas, 2003). These catastrophic

flood deposits are consistent with deposition

shortly after the impact event. It is possible that


these deposits are unrelated, but assuming that

these deposits are related to the AAT impact

event, it would suggest that the locations are

within approximately 750 km of the impact site,

after Collins, Melosh, & Marcus (2005).

2.20 Absence of a Crater: A recent crater that

is 43 ± 9 km in diameter (Glass & Koeberl,

2006) is sought. A structure on land should

form a distinctive morphological scar, which in

tropical regions would be expected to form of

a lake. The 1.83 km diameter, 0.576 Ma

(±0.047 Ma), Lonar Crater (Jourdan, Moynier,

Koeberl, & Eroglu, 2011; Schmieder & Kring,

2020) contains a 1.2 km diameter lake. The

10.5 km, 1.13 Ma (±0.10 Ma) (Jourdan, 2012;

Koeberl, Bottomley, Glass, & Storzer, 1997;

Schmieder & Kring, 2020) Bosumtwi Crater in

Ghana, again in a tropical region, contains an 8

km diameter lake. The only significant lake in

Indochina, Tonle Sap, was suggested as a

possible source crater by Hartung & Koeberl

(1994). Tektite distribution patterns and geoche-

mical regressions would indicate that this cannot

be the AAT source crater.

Given the absence of a lake, if the crater

were onshore, it would be impossible to erode

anything more than the most surficial part of a

relatively pervasive impact structure. Distinct

pyroclastic-like lithologies should be observed.

Igneous-like lithologies would have been

observed with deeper, but implausible, erosion.

Estimated denudation rates are 23 m to 393 m

since the AAT impact crater formed (Carter,

Roques, & Bristow, 2000; Jonell et al., 2017;

Yan, Carter, Palk, Brichau, & Hu, 2011) with

perhaps ± 75 m of erosion being a realistic

average value to use.

Destruction of the crater by tectonic

processes can be ruled out in the brief time since

impact. Tectonic processes may, however, have

enhanced sediment accommodation space,

assisting burial. Newly formed craters are natural

depocenters. Furthermore, post-impact, the crater

floor would be expected to continue to sag, e.g.,

Ries Crater experienced 134 +23/-49m of crater

floor subsidence lasting more than 600 ka (Arp et

al., 2021). Burial of the crater appears to be the

only viable option to hide a crater.

Burial by extensive flood basalts is a possi-

bility but would require a thick and extensive

area of ~1,450 km2 or more of post-impact age

lava flows to cover a ~43 km diameter crater.

Bolaven Plateau (seen in southern Laos in Fig.

6) is the only plausible (although sub-optimally

placed) volcanic center in the region of interest.

Bolaven lacks suitably extensive flood basalts

of a young post-impact age, allowing, at best, a

17 km diameter crater (Sieh et al., 2020), which

is 7 times less energetic than predicted, after

Collins et al. (2005), and more comparable with

the Bosumtwi impact that produced the much

smaller Ivory Coast Tektite strewn field.

Geochemical considerations have already been

discussed and raise objections for an AAT

impact into a pre-existing volcanic center.

Burial by sediments appears to be the only

plausible option to hide a crater. This could be by

river sediments or within a basin, such as the

YGH-SH Basin (Fig. 21). A river scenario is

somewhat problematic due to the raised crater

rim geometry that would more likely result in a

lake and diverted river system. A basin scenario,

with exceptionally high sedimentation rates,

readily explains the absence of a crater and is

entirely conceivable within the source region.

Sedimentation rates in the YGH-SH Basin were

estimated as 235 m/Ma in the late Miocene and

780 m/Ma in the Pliocene to Quaternary (Lei et

al., 2011). High sedimentation rates prior to the

impact readily explain the geochemical observa-

tions in tektites

2.21 Absence of an Ejecta Blanket: Whilst

there have been reports of an ejecta blanket in

and around the Bolaven Plateau (Sieh et al.,

2020; Tada et al., 2019) (Fig. 22), no convin-

cing evidence of a suevite deposits has been

presented. The presence of high shock / high

temperature tektites (Tada et al., 2019) in a low

shock, un-melted, monomict breccia deposit

suggests the crater is not nearby. The

monolithologic, cobbly / boulder sandstone

breccia (Sieh et al., 2020; Tada et al., 2019) is

unlike a proximal suevite, which characteristi-

cally yields partial melts. Furthermore, the

single represented lithology is a sandstone, which

is unsuitable from a REE perspective to be the

AAT source material. A localized mass transport

or flash flood origin might be more plausible,


Fig. 21: Regions of moderate sedimentation rates (green)

and high sedimentation rates (dark green), with a focus

on Quaternary sedimentation (Métivier, Gaudemer,

Tapponnier, & Klein, 1999). In terms of sedimentation,

the dark green regions have, by far, the highest

compatibility as a source region. Note that sedimentation

rates and depocenters have varied considerably over

time. The Yinggehai - Song Hong Basin is highlighted

by a black dotted line with the depocenter marked by a

black dashed line (Fan, 2018). The shelf break (500 m

contour) is shown as a black dot-dashed line (Liu et al.,

2016). Yellow shaded regions represent lower

probability for the presence of the AAT impact crater.

Inset: Data used in map overlay. Green = Probable

regions; Yellow = Less favorable regions for the AAT

impact.

either unrelated to the AAT impact or (to explain

a widespread occurrence) related in terms of

devegetation in the impact aftermath. An ejecta

blanket from a 43 km diameter crater would be

expected to be 100 m thick at 16 km, 20 m thick

at 43 km, 10 m thick at 60 km, 5 m thick at 81

km, and 1 m thick at 154 km from the rim of the

post-impact crater. The described ejecta blanket

is suggested to be 40-50 m thick (Sieh et al.,

2020) based on the depth of incised stream

valleys as opposed to direct observations. Tada et

al. (2019) suggests an ejecta blanket ranging

from under 1 m to a maximum of 9 m thickness.

Sieh et al. (2020) models a much smaller impact

of maximum 17 km diameter, which better fits

with the proposed thinner ejecta blanket but fails

to explain the widespread distribution and

abundance of AAT. Finally, Sieh et al. (2020)

elected not to perform a detailed study of planar

deformation features in quartz grains, a

diagnostic test (but not discounting reworking),

instead relying on undiagnostic lithological

observations of the deposit and the circular

argument of proximity to an unproven crater. The

proposed Bolaven ejecta blanket was not utilized

in the map overlay, pending further evidence.

Tada et al. (2019) noted in their poster that

the AAT proximal ejecta blanket has never

conclusively been identified on land in Indo-

china. This observation remains true. Tada et al.

(2019) went on to note that the ejecta deposit is

important to constrain the impact location.

Indeed, the absence of an ejecta blanket may be

a constraining factor. It is difficult to envisage

that all traces of an ejecta blanket have been

eroded away. A more plausible explanation for

the apparent absence of an ejecta blanket, is that

the thick proximal ejecta deposit is located

offshore (Fig. 22). If only a thin ejecta blanket

was present onshore, then it is realistic that it

could have been entirely eroded or reworked.

The absence of an ejecta blanket suggests the

point of impact is far from the current shoreline:

probably at least 50 km (as conservatively

depicted in Fig. 22), and more likely over 80 km

(resulting in up to a 42 m and 10 m thick ejecta

layer, respectively, on the current land surface,

pre-erosion).

3. Conclusions

Multiple lines of independent data indicate

that the AAT source crater will be found in the

Gulf of Tonkin to central-eastern Indochinese

region as opposed to ~800 km further north-

northwest as would be implied if all tektites were

downrange ejecta. Accepting a Gulf of Tonkin to

central-eastern Indochina source region implies

the existence of uprange tektites. The AAT impact

was unarguably oblique and as such there should be

a distinct uprange zone of avoidance in the early

phase of impact (Gault & Wedekind, 1978;

Schultz et al., 2009, 2007). Consequently, uprange

tektites must be from a marginally later stage of

impact. With reference to the calculated AAT

crater diameter of 43 ± 9 km (Glass & Koeberl,

2006) and to ejection velocities in Artemieva

(2008) it must be assumed that the uprange ejecta,

for it to be present, must be deeply excavated.

From the 10Be content of these uprange tektites it


must be concluded that a thick sequence of recent

sedimentary rock has been sampled. This is

indicative that the impact occurred in a pre-

existing depocenter. The source crater location is

thus largely restricted to the Yinggehai - Song

Hong (YGH-SH) Basin. A YGH-SH Basin

impact is not only in keeping with all available

data, but the young, rapidly deposited, water

saturated, siliciclastic sediment with saline

formation water / sea water readily explain the

abundance and geographic extent of the AAT.

Furthermore, continued exceptionally high

sedimentation rates in accommodation space

created, in part, by the impact itself and

subsequent sagging, would have resulted in rapid

burial of the crater by hundreds of meters of

sediment, thus explaining the apparent absence of

the AAT source crater and its thick proximal

ejecta blanket.

The principles of map overlay (McHarg,

1969) can be utilized to combine data and

determine the most probable location of the AAT

source crater. Some of the data presented and

utilized is conflicting, e.g., the Jurassic versus

recent (Rb/Sr versus 10Be) age of the source rock.

With perfect data sets all overlay map evidence

will overlap on a central point. With more patchy

or ambiguous data the overlap becomes partial or

overlay elements become isolated, indicative that

at least one of the lines of evidence is incorrect or

insufficiently resolved. The nature of the partial

data set for tektites, most critically for proximal

tektites in the Gulf of Tonkin and South China

Sea region, will result in error and a degree of

skewness of the data. The use of multiple lines

of evidence means that each observation only

comprises a small percentage of the data set.

Potentially misleading data should be overwhel-

med by the weight of data, which, on average,

should be correct.

An overlay map was constructed by placing

maps of the same scale on top of one another. Fig.

23, constructed from all positive and negative

data, utilized a total of 42 overlays (25 green, 15

yellow, and 2 red) taken from the insets in Figs.

1 - 6, 10, 12 - 17, & 19 - 22. White (no data)

regions were transparent, green and yellow data

regions were 90% transparent, whilst red data

was weighted at 70% transparency. The green

Fig. 22: Expected ejecta thickness from a 43 km dia-

meter crater (black dashed lines). The crater position

(Whymark, 2013) is for example only as the crater

location is not established. In consideration of the

absence of an ejecta layer onshore (either patchy or

continuous), there is a higher probability that the

impact was, conservatively, at least 50 km offshore

from the current coastline (and likely more). A

continental shelf region over 50 km from the current

shoreline is depicted as a green shaded area. An

unconfirmed ejecta layer was identified (Tada et al.,

2019) (green lines centered on southern Laos). The

breccia layer (Unit 2) reached a maximum thickness

of 9 meters in the Bolaven Plateau. This unconfirmed

ejecta layer was not utilized on composite overlay

maps. Inset: Data used in map overlay. Green =

Probable regions for the AAT impact.

Fig. 23: Combined positive and negative data for source

crater location. Greener areas = higher probability.

Yellower areas = lower probability. Red / orange areas =

no probability.


shaded areas = higher probability, yellow shaded

areas = lower probability, and red / orange

shaded areas = no probability for the crater being

in the region. Fig. 24, utilized only negative data,

using 17 overlays (15 yellow, and 2 red) taken

from the insets in Figs. 1, 4 - 6, 10, 12 - 17, & 19 -

21. White (no data) regions were transparent,

yellow data regions were 50% transparent and

red data was opaque. A blue background was

added to highlight the most probable region of

impact (blue). A region in the center or northwest

segment of the Gulf of Tonkin had the least

objections as an impact location, with a broader

swathe encompassing the Gulf of Tonkin and

central-eastern Indochina being plausible (Figs.

23 & 24). The most probable impact location,

considering positive and negative data, is within

~100 km of E107.20°, N18.30°, but not

(significantly) in a landward direction. The

likelihood that the impact occurred in a

depocenter with high sedimentation rates would

indicate a basinward impact location (see Fig. 24

for the YGH-SH Basin depocenter).

A possible structure exists in the YGH-SH

Basin at E107.85°, N17.78° (Whymark, 2013,

2018). This depocenter region is known as the

‘Great Sag’ (Clift & Sun, 2006). Evidence of the

presence of a crater include a 43 km diameter

annular gravity anomaly (Whymark, 2013,

2018). A circular region of shallow-rooted

chaotic seismic from approximately the time of

impact to the late Miocene (Gong & Li, 2004;

Gong et al., 1997; Yan et al., 2011). A circular

pattern of shale diapirs (Lei et al., 2011, 2015)

which may relate to post-impact geothermal

activity conducting fluids along lines of

weakness. An outer elliptical pattern of shale

diapirs, possibly indicating significant slumping

of the suspected crater, as would be anticipated

from an oblique impact crater with asymmetrical

depth profile in a continental shelf setting. A high

geothermal gradient (Lei et al., 2011) may record

the residual heat from the impact event. Seismic

line 0755 (Lei et al., 2015, Fig. 3) (supported by

Figs. 1.3.2.6 & 1.3.2.7 in CCOP, 2008) is

apparently consistent with an impact crater

(onlap, rim fault, and chaotic seismic). Further

seismic lines have been recorded over the

potential crater (Lei et al., 2015; CCOP, 2008)

but are of poor resolution or are not in the public

domain. Overlay of YGH-SH Basin geophysical

and well data would narrow the search for the

AAT source crater. Efforts to locate the AAT

source crater must shift from improbable and

fruitless onshore regions to the highly probable

YGH-SH Basin.

Acknowledgments

This project was self-funded. Thank you to

Dr. J. Rimando for advice and to anonymous

reviewers for constructive suggestions that

enhanced this article.

Note

The author remains neutral regarding juris-

dictional claims in maps and geographic nomen-

clature

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30 Thai Geoscience Journal 2(2), 2021, p. 30-37


ISSN-2730-2695; DOI-10.14456/tgj.2021.3

The ‘new normal’ for geoscience in a post-COVID world:

connecting informed people with the Earth

Steven M. Hill*, Jane P. Thorne, Rachel Przeslawski,

Rebecca Mouthaan, and Chris Lewis

Geoscience Australia, Canberra, Australia.



Abstract

We consider how our society can use data, information and knowledge of the Earth under a broad

definition of geoscience to better connect with the Earth system. This is important in our changing

world, in particular how geoscience contributes to our response to the societal impacts of the

COVID-19 pandemic. Ultimately, informed decisions utilizing the best geoscience data and

information provide key parts of our economic, environmental and cultural recovery from the

pandemic. The connection to country and more widely connection to our planet and the greater

Earth system that comes from personal experience has been especially challenged in 2020. Much

of Australia’s population have been encouraged to stay in our homes, first because of major fires

and more recently in response to isolation from the COVID-19 pandemic. Although domestic

travel became increasingly allowable, international travel has been restricted for much longer.

This has increased the importance of trusted data and information initially from domestic locations

and for more extended time between countries that are now less accessible. We discuss ways that

geoscience governs our discovery and use of minerals, energy and groundwater resources and

builds resilience and adaptation to environmental and cultural change. A broad definition of

geoscience also includes positioning and location data and information, such as through integrated

digital mapping, satellite data and real-time precise positioning. Important here is sharing, with

two-way exchange of data, information and knowledge about the Earth, through outreach in

geoscience education programs and interactions with communities across Australia, into

neighboring countries in Asia and the Pacific, and across the world. An aspiration is for geoscience

to inform social license through evidence-based decisions, such as for land and marine access, for

a strong economy, resilient society and sustainable environment. At Geoscience Australia, we

have developed a ten years strategic plan (Strategy 2028) that guides us to be a trusted source of

information on Australia’s geology and geography for government, industry and community

decision making. This will contribute to a safer, more prosperous and well-informed Australia and

its connection to neighbouring countries, such as in Asia, as well as people that are better

connected to country and our planet.

Keywords: community education and outreach, earth system science, environment, geoscience, mapping,

resources

1. Introduction

The importance of trusted, high-quality and

relevant science to inform and advise govern-

ments and our communities is greater now than

it ever has been. This is particularly the case for

geoscience and its role to guide people’s

connection to the Earth as the place where we

live and obtain the resources we need to live our

lives. Our community’s recognition of the value

of geoscience ensures the future viability and

evolution of geoscience and it’s ability to

contribute to informed impact in our nations, and

our planet. This recognition, however, is not to

be presumed (or assumed). The world changes

and as such the roles and perceptions of

geoscience need to evolve and adapt for its

continued resilience and relevance.

This paper has three main parts:


Steven M. Hill et al. / Thai Geoscience Journal 2(2), 2021, p. 30-37 31

1. It considers how geoscientists project

and define themselves in society and suggests

that a broad definition of geoscience within a

greater Earth system has greater value than

more narrow, specialized foundations;

2. Demonstrations of how Geoscience

Australia strategically supports and develops its

science as part of the broad context of geoscience

within an Earth system for maximum impact and

value; and,

3. Consideration of how this approach is

being developed in response to the post-COVID

demands of our society and their connection to

our planet.

2. Geoscience in the Earth System

Traditionally in Australia there has been an

emphasis on the links between geology, geolo-

gists and our resources industry, particularly for

mineral commodities such as iron ore, gold and

base metals, but also energy commodities such

as coal, oil, gas, and uranium. This largely

reflects the importance of this industry for

export earnings and our nation’s prosperity.

This has meant that the projection of the role of

the geologist has not been challenged so much

in the past as it is today. Rather than the vision

of mining to express progress and prosperity

there is now a greater call for the industry to be

viewed on the basis of more trusted equitable

and ethical criteria and the sustainable public

value of the industry for not only the economy

but also the environment and community. This

includes assessment and visibility of the entire

resources chain from investment, exploration,

mining, and the destiny (such as uses, recycling

or reuse) of the resources. This broader

perspective calls for a broader context of our

science of the Earth that extends beyond just

rocks and resources but into the broader field of

geoscience.

Geoscience embodies the science of the

Earth. It especially includes but extends beyond

geology to also include fields of geography,

geodesy, Earth observation, marine science,

pedology, geophysics, geochemistry, geoha-

zards, and many parts of climatology, ecology,

hydrology, space and planetary science and,

environmental science. Geoscience investigates

the past, measures the present and models the

future behavior of the planet. It links closely

with the biological, chemical and physical

sciences as part of Earth system science (Steffen

et al., 2020), to include a holistic view on

interactions and dynamic processes between ice,

rocks, water, air and life.

3. Geoscience Australia: role and science

At Geoscience Australia we embrace the

broad perspective of geoscience, not just in our

name, but in the strategic planning of our role,

activities and our science. Geoscience Australia

is Australia’s national public-sector geoscience

entity. We provide advice on the geology and

geography of Australia to support progress,

growth, and investment towards a safer, more

prosperous and well-informed Australia. Our

main stakeholders include government, industry

and the community.

Our decadal strategy, Strategy 2028, sets

out the impacts our work will have over the

next decade under six key areas:

1. Building Australia’s resource wealth.

Australia has a rich and diverse mineral and

energy endowment, which is a major contributor

to the nation’s wealth, economically and socially.

The provision of high quality regional-scale

geoscience data and information lowers the

risks of exploration, advanced exploration,

mining and processing technologies;

2. Supporting Australia’s community safety.

Providing disaster risk information to help

Australians understand the consequences of

hazard events, which contributes to more

resilient communities now and in the future;

3. Securing Australia’s water resources.

Supporting the fair sharing of water resources by

identifying the location, quantity and quality of

groundwater resources to support sustainable

water management in the driest inhabited conti-

nent;

4. Managing Australia’s marine jurisdictions.

Including baseline mapping, understanding of

marine resources and assets, and the ability to

measure change over time;

32 Steven M. Hill et al. / Thai Geoscience Journal 2(2), 2021, p. 30-37

5. Creating a location-enabled Australia.

Providing information on when and where

events and activities occur is essential to make

decisions and improve economic, environmental

and social outcomes. This includes delivery of

real-time precise positioning, digital location

information and Earth observation from satellite

data platforms; and,

6. Enabling an informed Australia. Delivering

world-class, trusted data and platforms and

expertise to support high-impact geoscience,

transparent evidence-based decisions and social

licence to operate. This includes our education

and science outreach programs.

To achieve these strategic impacts we need

to be the best people and organization that we

can as well as ensure that we have a strong

foundation of excellent and relevant science.

The Geoscience Australia Science Principles

describe how we conduct science in both long-

term planning and day-to-day operations. The

six Science Principles are:

1. Relevant science to ensure that Geoscience

Australia provides quality assured information to

the right people in the right timeframe so they can

make evidence-based decisions, particularly

related to the Australian Government. This

includes the provision of scientific advice to meet

national and international obligations (e.g. Paris

Climate Agreement,Australia New Zealand

Foundational Spatial Data Framework and

United Nations Integrated Geospatial Infor-

mation Network, Offshore Petroleum and

Greenhouse Gas Storage Act 2006, and the

United Nations – Global Geodetic Reference

Frame Sustainable Development Goals, and

Sendai Framework for Disaster Risk Reduction).

2. Collaborative science to allow Geoscience

Australia to meet emerging challenges that are

more complex than any single individual, team

or agency can achieve. This requires us to

engage with not only the broader research and

data community, but also non-scientific stake-

holders who are more likely to use and value our

information if they are involved in our work.

3. Quality science to maximise stakeholder

confidence that the data and information we

provide is accurate, results are repeatable, and

any uncertainties are explained and accounted

for. All of these mean our science reflects not just

quality, but integrity. Data and information can

then be used to inform current decisions and

debate, and be re-used and re-purposed long after

it is created. As both a government agency and a

member of the Australian research community,

we have key compliance requirements, including

the Australian Code for the Responsible Conduct

of Research.

4. Transparent science to demonstrate that

our scientific activities are unbiased and reflect

commitment to extend the role that science plays

in the transparency of Australian Government

processes (e.g. Principles on Open Public Sector

Information, Declaration of Open Government).

By openly sharing our work and abiding by the

FAIR data principles (findable, accessible, inte-

roperable, reusable) we create a platform that

supports further innovation in the tradition of

scientific discovery.

5. Communicated science to ensure that

Geoscience Australia’s scientific data and

information is accessible to and understandable

by a variety of stakeholders. By tailoring the

communication of scientific information to a

particular audience and purpose, Geoscience

Australia’s scientific work can be valued by

stakeholders. This also means communicating

appropriate background knowledge to stake-

holders and the public to increase their

capability to understand complex ideas often

associated with scientific research. Part of

communication here also involves active

listening, particularly to ensure that stake-

holder’s matters of concern and their needs are

well understood.

6. Sustained science capability to undertake

scientific activities that meet current and future

strategic priorities. The type and level of science

capability we retain in-house is inherently

controlled by strategic demands and available

budget. It is also dependent on technical and

business capabilities such as information

management, outreach and education, enginee-

ring, and communication.

Three examples of major projects from

Geoscience Australia’s work program are

briefly outlined as well as their impact and

value for our nation. These include:


i) Positioning Australia;

ii) Digital Earth Australia (DEA); and,

iii) Exploring for the Future (EFTF).

i. Positioning Australia

The Positioning Australia Program is

developing a world-leading satellite positioning

capability, which many refer to as GPS (Global

Positioning System). The program will provide

accurate, reliable, and real-time positioning

across Australia. It will enable increased

productivity, new and innovative technologies,

and accelerate economic growth, particularly for

regional Australia and businesses.

The program encompasses the National

Positioning Infrastructure Capability (NPIC)

and a Satellite Based Augmentation System (or

SBAS) and is underpinned by the Australian

Geospatial Reference System. Currently, we

can know our position on the Earth within 5-10

metres of accuracy. By upgrading our existing

ground stations, we will improve our posi-

tioning accuracy to within 3-5 centimetres. We

are doing this by building the physical and data

infrastructure and analytics capabilities to

deliver 3 things:

1. 10 cm accuracy of positioning across

Australia and its maritime zones

through SBAS;

2. 3-5 cm accuracy of positioning for

areas with mobile phone coverage, in

particular regional and metropolitan

areas, through NPIC; and,

3. Open-source tools and software to

support use of positioning, navigation

and timing services.

This work is vital for the next wave of

innovation, from location-based automation or

artificial intelligence, to augmented reality.

Positioning Australia is fundamental in suppor-

ting the transformational technologies that will

benefit our economy.

To trial this, we established 27 SBAS

projects across 10 industry sectors including

agriculture, aviation, construction, consumer,

resources, road, rail, maritime, mining and

water utilities. Based on the SBAS trial across

10 industry sectors, we have estimated the

economic value of our positioning program.

An independent report, which investigated the

benefits of SBAS, found that it would create

A$6.2 billion of value over 30 years; over

A$200 million p/a economic benefit initially,

with plenty of upside across a range of sectors.

The benefits included:

• Improving the efficient spraying of =

water on farms (by between 1 and 7%)

by being able to spray exactly where

water is needed;

• Finding injured patients to facilitate

helicopter rescues more effectively;

• Enabling intelligent transport systems,

to reduce road fatalities;

• Improving safety at mine sites; and,

• Supporting virtual fencing to manage

livestock better.

It is also important to note that we expect

there will be uses that we have not thought of

yet, enabling innovation and new businesses to

start and flourish

ii. Digital Earth Australia (DEA)

In the DEA program, we are transforming

satellite imagery into insights about changes in

Australia’s natural and built environments. DEA

provides access to high quality satellite imaging

of the Earth’s surface, to detect physical changes

across Australia in unprecedented detail,

including soil and coastal erosion, crop growth,

water quality, and changes to cities and regions

over time. It gives farmers, land managers,

industry, and governments the information they

need to make better decisions about how they

optimise the use of their resources.

DEA will benefit users that need accurate

and timely information on the health and

productivity of Australia’s landscape. It will

support government and industry to better

monitor change, to protect and enhance

Australia’s natural resources and enable more

effective policy responses to natural resource

management problems. Information extracted

from satellite images of the Earth will assist

emergency managers in real time during

disasters like bushfires and floods. It will assist

in more productive farming and enable

informed decision making across governments.


iii. Exploring for the Future (EFTF)

Through the EFTF program, we are

building a prospectus of mineral, energy, and

groundwater resources for Australia. The

program launched in 2016, and the first four

years of work has focused on northern

Australia, using innovative techniques to map

the surface and image deep into the Earth,

developing a much better understanding of

Australia’s resource potential.

The first phase of the EFTF program set out

to address the strategic need for more

geoscience information in northern Australia.

Some 21 projects have delivered over 250 new

datasets and technical reports, covering more

than 3 million square kilometres of the

continent, and creating images of the Earth’s

crust and upper mantle, down to 200 kilometres

depth, assisting in identifying the regional-

-scale systems that result in the creation of ore

deposits, oil and gas fields and groundwater

resources.

All of these data are freely available through

our digital catalogue and world-leading data

discovery portal. The portal includes innovative

3D visualisation and analytical tools that can

create maps to support analysis and decision-

making. The portal can be visited at eftf.ga.gov.au.

The EFTF program has changed perceptions

and behaviours in the minerals and petroleum

industries, with the program’s pre-competitive

data and information translating into real

impacts. For example, since 2018, 17 companies

have acquired new exploration acreage in the

region in between Tennant Creek and Mount Isa

covering more than 100,000 square kilometres.

This uptake of exploration tenements and the

investment that follows, can be linked back to

Geoscience Australia’s program activities and

outputs. Importantly, this new interest is in

‘greenfield’ areas—locations that have only seen

limited exploration in the past. Nearby, the

program has also stimulated work program

commitments valued at close to $100 m in the

South Nicholson Basin, an emerging petroleum

play on the Queensland Northern Territory

border. An independent analysis of the EFTF

program’s projected economic impacts indicates

that the return on the government’s investment

will be substantial. The report considered three

projects representing $40 million of investment

under the program. The returns from the potential

discovery and development of new mineral and

energy resources were estimated by ACIL Allen

to range from $446 million under the most

conservative modelling to more than $2.5 billion

under the most optimistic modelling.

The first phase of the program created

hundreds of jobs, through more than 300

contracts worth $69.4 million. This included the

creation of 11 jobs for Indigenous Australian

trainees in Alice Springs, processing geological

samples with the Centre for Appropriate

Technology—a not-for-profit Aboriginal and

Torres Strait Islander company. Any invest-

ments in mining and agricultural operations will

also create further opportunities for employment

in regional Australia, supporting economic

recovery in regions where opportunities may

otherwise be limited. Large mines can directly

employ thousands of people and indirect

employment can be several times that.

Importantly, this brings with it the opportunity

for significant levels of employment for

Indigenous Australians in regional areas. These

benefits further demonstrate the importance of

the resources sectors as “engines” of the

Australian economy – engines that are needed

more than ever in the economic recovery from

the COVID-19 pandemic.

The outcomes and impacts from the first

phase of EFTF have inspired the extension of

EFTF for a second phase. In June 2020, this

program received a $125 million extension and

expansion over the next four years. The

emphasis of this phase is to take the program

national. While the work will be extended into

southern Australia, two corridors that extend

north-south across the continent will ensure

continued focus on prospective regions in

northern Australia. This is a fantastic oppor-

tunity to continue our use of innovative

geoscientific techniques to expand the national

coverage of key datasets and to take more

detailed looks into new regions to encourage

further greenfield exploration. Through encou-

raging investment, the program will contribute

towards the nation’s post COVID-19 economic

recovery, creating jobs where they are needed


in regional and remote communities both now

and into the future.

4. Geoscience in response to change following

COVID-19

COVID Change and Challenge

The COVID-19 pandemic has brought

obvious illness and death to our world, but it

has also brought challenges for our industries

and economies, employment, travel and most

particularly it has challenged the mental health

of people and communities. For many it has

created a new experience of uncertainty and

loss of control of their lives, and as such has

been a reminder that our society and the world

changes. We live in interesting times and

probably the most inevitable feature of our time

is “change”. Key here is going to be how we

are resilient, how we adapt, but most of all how

we adopt changes as opportunities.

One challenge that we still have to adapt to is

how we will maintain and grow our “connection”

within our community of scientists and extend

that into our society. Most particularly how we

best live and connect to our country and the

nation and planet in which we live. In Australia,

domestic travel within states and territories has

flourished (particularly for tourism), however,

interstate travel has had the risk of uncertainty

due to border closures, while international travel

has been extremely limited. With busy lives and

then lockdowns and border closures and other

pressures, maintaining and growing our

connection to country and planet will challenge

us. This leaves us open to risks of mis-

information about regions and nations that we are

now have less physical connection.

Indigenous Science

We have much to learn from indigenous

people and their connection to country but also

their traditions of respect and passing on skill

and knowledge related to country. How many

in our increasingly urban society understand

where they live in relation to geology,

geography and landscape? Despite the amount

of landscaping and concreting, asphalt and

artificial lawn that we cover the ground with,

we still live as part of an active and changing

Earth system.

Indigenous science incorporates traditional

knowledge and perspectives that have built on

thousands of years of observation and experi-

mentation, and then may be combined with more

conventional scientific methods. Indigenous

science is typically expressed as observations,

know-how, practices, skills and innovations.

Previously it has been recognised in applications

for agriculture, land management, ecology and

medicine, although emerging potential exists in

geoscience applications.

With much of this work being implemented

in regional and remote areas we are also building

opportunities to partner with indigenous commu-

nities, encouraging indigenous participation by

sourcing goods and resources directly through

local communities. Our motivation is to develop

and sustain respectful and meaningful relation-

ships, build local indigenous capacity and

contribute to local economic development for

mutual benefit.

Our best people and science to meet the

challenge

To meet the challenges of a changing world,

our science is more important than it has ever

been, especially because of the risk of mis-

information and poor decisions about country

and places that we are less connected with. Skill

and knowledge will be important here but so too

how we make our data and information

accessible as well as ensuring that we provide

“fit-for-purpose” and relevant data and inform-

ation for making efficient and connected

decisions about our country.

Education and communication of our

science will be important here. Geoscience

Australia maintains an active and engaging

geoscience education and outreach program

with visiting school groups but also an

increasing amount of online teaching materials

and delivery. In 2019 our education centre

hosted visits from over 11,300 students and

1050 teachers, and although the centre was

closed for on-site visits for much of 2020, our

online delivery into schools reached out to

many more than this. We are also making our


national collection of minerals and fossils more

accessible via online “galleries” and associated

information. One example of this is our online

Google Arts and Culture exhibit of “Minerals

in ModernTechnology” (https://artsandculture

.google.com/story/RQXxTbNbs585MQ).

This also is reflected in the respectful way

that we access land and marine areas to conduct

our science, and as part of this, Geoscience

Australia has recently established a Land and

Marine Access team (LAMA) to lead us on a best

practice approach in this area. It is increasingly

important that this access is legally compliant but

also prevents harm and includes timely and

accountable record keeping, such as access

agreements. A key component here is that access

is purposeful, transparent, effective and

inclusive. This means that all stakeholders

interested in, or affected by field activities will be

engaged using the most appropriate communi-

cation channels and language. Communication

will be open and honest, seeking to build trust

and credibility. Engagement will occur early in

the planning process and will continue

throughout the project life cycle, providing

opportunities for stakeholders to ask questions,

seek clarification and to contribute their own

experiences and information. The field access

cycle will be closed by all data obtained by field

activities being delivered back to those

communities that have been impacted by data

acquisition.

Whilst communication and education are

important pursuits we also need to bring our

best ears and actively listen to the community

and their matters of concern that we are trying

to engage with (e.g. Stewart & Lewis, 2017).

We must continue to nurture an inclusive

culture in our geoscience community, to ensure

that all of us feel we can belong, that we are

valued for who we are as well as our know-

ledge, skills and experience. This includes

providing equal opportunities to participate,

contribute and progress. To maximise our

opportunities for success we need to tap into

the full breadth and diversity of expertise,

people and talent that we possess across our

geoscience community and our science

partners. This not only makes us better people

and provides a better place to work but also

improves scientific outcomes and innovations,

such as through contributions from our

cognitive diversity and the novel questions,

new discoveries, and greater networks and

connections that come from that (Medin & Lee

et al., 2012; Dutt, 2019; Handley et al., 2020;

Hanson, Woden, & Lerback, 2020).

5. Conclusions

We hope that it has given you some new

insights and perspectives on how a definition

of ourselves as geoscientists within the context

of a broader Earth system can bring higher

impact and value to our nation, neighboring

countries, such as in Asia, and across the world.

Let’s bring our best and most connected person

to achieve better geoscience!

Acknowledgements

This paper has been published with

permission of the Chief Executive Officer of

Geoscience Australia. The authors acknow-

ledge the insights and benefits from discussions

with other staff at Geoscience Australia. We

also thank the organizers of the CCOP Thematic

Session (56th CCOP Annual Session) for provi-

ding the opportunity to present this orally and

now as a written manuscript. Feedback and

discussion with delegates of CCOP conference

following the oral presentation have also been

valuable and inspirational.

We acknowledge the owners and commu-

nities, including aboriginal communities whose

land and sea country that we have worked on to

conduct our geoscience. Our collaboration with

Australia’s state and territory governments have

also been important for enabling our geoscience

to have its value, impact and connection.

References

Dutt, K. (2019). Race and racism in geosciences. Nature

Geoscience, 13, 2-3. https://doi.org/10.1038/s41561-

019-0519-z

Handley, H.K., Hillman, J., Finch, M., Ubide, T.,

Kachovich, S., McLaren, S, Petts, A., Purandare, J.,

Foote, A. & Tiddy, C. (2020). In Australasia, gender

is still on the agenda in geosciences. Advances in

Geoscience, 53, 205-226. https://doi.org/10.5194/

adgeo-53-205-2020

https://artsandculture.google.com/story/RQXxTbNbs585MQ

https://artsandculture.google.com/story/RQXxTbNbs585MQ


Hanson, B., Woden, P. & Lerback, J. (2020). Age,

gender and international author networks in the Earth

and space sciences: implications for addressing

implicit bias. Earth and Space Science, 7(5). https://

doi.org/10.1029/2019EA000930

Medin, D.L. & Lee, C.D. (2012, April). Diversity makes

better science. Association for Psychological Science

Observer, 25(5). Retrieved from https://www.psycho-

-logicalscience.org/observer/diversity-makes-better-

science

Steffen, W., Richardson, K., Rockstrom, J., Schell-

-nhuber, H.J., Dube, O.P., Dutreuil, S., Lenton, T.M.

& Lubchenco, J. (2020). The emergence and

evolution of Earth System Science. Nature Reviews

Earth & Environment, 1, 54-63. https://doi.org/

10.1038/s43017-019-0005-6

Stewart, I.S. & Lewis, D. (2017). Communicating con-

-tested geoscience to the public: moving from

‘matters of fact’ to ‘matters of concern’, Earth-

Science Reviews, 174, 122-133. https://doi.org/10.

1016/j.earscirev.2017.09.003



ISSN-2730-2695; DOI-10.14456/tgj.2021.4


Susumu Nonogaki* and Tsutomu Nakazawa Geological Survey of Japan, AIST, Tsukuba, Japan



Abstract

The Geological Survey of Japan (GSJ) carried out 3D geological mapping of central Tokyo. In

this project, we performed surface-based geological modeling using borehole logs created by GSJ

and also those provided by local governments as well as the development of the Web system for

sharing 3D geoinformation. The 3D geological map of central Tokyo will be released on the

“Urban Geological Map” website in a year. In this paper, we describe the current progress of this

project.

Keywords: borehole logs, geotechnical properties, Tokyo, voxel model, 3D geological map.

1. Introduction

Recently there is growing demand for

subsurface information to contribute to the

evaluation of geological risk, such as liquefaction

and amplification of ground motion, in urban

areas in Japan due to frequent disasters caused by

large-scale earthquakes. To meet this demand,

GSJ has carried out a 3D geological mapping

project since 2013. In the project, we create 3D

geo-information based on detailed stratigraphic

studies and on computer modeling of subsurface

geological structures and make it open to the

public on the Internet. To date, we have created a

3D geological map of the northern Chiba area,

eastern part of Tokyo metropolitan area (Naya et

al., 2018), and released it on the “Urban

Geological Map” website (https://gbank.gsj.jp/

urbangeol/index_en.html). As the next stage of

this work, we are carrying out 3D geological

mapping of central Tokyo, cooperating with the

Civil Engineering & Training Center (CETC) of

the Tokyo Metropolitan Government. In this

paper, we describe an outline of the 3D

geological mapping method and summarize the

current progress of the work.

2. Methodology

The study area comprises the special wards

of Tokyo, Japan (Fig. 1). This area geologically

consists of three parts: upland with Pleistocene

deposits, lowland with Holocene deposits, and

reclaimed land along the coast. In this area, there

are more than 60,000 borehole logs created for

public construction works. The borehole logs

are accumulated as XML files by CETC. Most

of them have simple lithofacies descriptions

and Standard Penetration Test results (SPT N-

values). In our project, we utilize these

borehole logs to assess the subsurface geology.

Fig. 2 shows a flow diagram of the 3D

geological mapping. In the mapping, we perform

(1) establishment of a standard stratigraphic

framework, (2) stratal correlation using borehole

logs, (3) surface-based geological modeling,

and (4) release of the map on the Internet. The

details of each process are described below.

2.1 Establishment of standard stratigraphic

framework

A standard stratigraphic framework beneath

central Tokyo is established based on high-

quality stratigraphic data obtained from

drilling surveys and laboratory work by GSJ.

The stratigraphic data includes detailed core

descriptions such as sedimentary facies, tephra

marker layers, and fossils, 14C age measurement,

and PS velocity and density logging.

2.2 Stratal correlation using borehole logs

Stratal correlation between borehole logs

obtained from past construction work is carried out

by adopting the standard stratigraphic frame work.

In order to increase the efficiency of the stratal

correlation process, voxel models of geotechnical

properties, such as lithofacies and SPT N-values,

are constructed from a large number of borehole

logs based on Nonogaki et al. (2020) and are used


https://gbank.gsj.jp/urbangeol/index_en.html

https://gbank.gsj.jp/urbangeol/index_en.html

Susumu Nonogaki and Tsutomu Nakazawa/ Thai Geoscience Journal 2(2), 2021, p. 38-42 39

Fig. 1: Study area. Solid red lines indicate the special wards of Tokyo, Japan. Base map is based on the Fundamental

Geospatial Data (DEM 5-m-mesh Elevation) (Geospatial Information Authority of Japan, 2019) and the Seamless

Digital Geological Map of Japan 1:200,000 (Geological Survey of Japan, AIST, 2020).

Fig. 2: Flow diagram of 3D geological mapping.

40 Susumu Nonogaki and Tsutomu Nakazawa/ Thai Geoscience Journal 2(2), 2021, p. 38-42

Fig. 3: Example of stratal correlation with voxel model of geotechnical properties. Lithofacies derived

from voxel model is displayed in broken red line frames.

Fig. 4: Example of vertical cross-section images of geotechnical properties in the upland area. (a) index

map showing Setagaya wards, Tokyo, (b) topographical map, (c) cross-section image of voxel model of

lithofacies, and (d) cross-section image of voxel model of SPT N-values. (a) was based on the National

Land Numerical Information (administrative boundary) (Geospatial Information Authority of Japan,

2020). (b) was based on the Fundamental Geospatial Data (DEM 5-m-mesh Elevation) (Geospatial

Information Authority of Japan, 2019).

Susumu Nonogaki and Tsutomu Nakazawa/ Thai Geoscience Journal 2(2), 2021, p. 38-42 41

as auxiliary data for the data for the correlation

process (Fig. 3).

2.3 Surface-based geological modeling

The Digital Elevation Models (DEMs) of the

geological boundary surfaces are generated by

the spline fitting method (Nonogaki, Masumoto

& Shiono, 2012) using the results of stratal

correlation. Additionally, based on Shiono,

Masumoto & Sakamoto (1998), a surface-based

3D geological model is constructed by combi-

ning the DEMs with a consideration of the

geological history.

2.4 Release on the Internet

The 3D geological model is available to the

public on the “Urban Geological Map” website.

On the website, the user can browse 2D and 3D

geological map and borehole logs used for

mapping as well as being able to create geologi-

cal cross-sections along arbitrary lines.

3. Current progress

We constructed voxel models of lithofacies

and SPT N-values to a depth of several tens of

meters in the study area and finished stratal

correlation of about 50,000 borehole logs.

Moreover, we generated the DEMs of nine

geological boundary surfaces using the result of

stratal correlation and constructed a provisional

3D geological model of central Tokyo

comprised of ten geological layers. The spatial

resolution (grid size) of each DEM is five

meters. Fig. 4 shows the vertical cross-sections

of the voxel models in Setagaya ward. The

cross-sections reveal that soft muddy sediments,

which have high risk of amplifying earthquake

ground motion, underlay hard gravel bed in the

upland area. Fig. 5 shows aprovisional 3D

geological model of central Tokyo. The geolo-

gical model also clearly shows the distribution

pattern of some geological layers which have a

risk of natural disasters.

4. Conclusions

The 3D geological map of central Tokyo is

expected to contribute to increasing the accuracy

of geological risk evaluation. Furthermore, it is

also helpful for planning urban infrastructure,

analyses of groundwater flow, and for the real

estate business. The 3D geological map of central

Tokyo will be released in 2021.

References

Geological Survey of Japan, AIST (2020). Seamless

Digital Geological Map of Japan 1:200,000, January

2020 version [online] (in Japanese). [Cited 20

January 2021]. https://gbank.gsj.jp/seamless/.

Geospatial Information Authority of Japan (2019).

Fundamental Geospatial Data (DEM 5-m-mesh

Elevation), July 2019 version [online] (in Japanese).

[Cited 20 January 2021]. https://fgd.gsi.go.jp/down

load/menu.php.

Geospatial Information Authority of Japan (2020).

National Land Numerical Information (Administra-

-tive boundary), October 2020 version [online] (in

Japanese). [Cited 20 January 2021]. https://nlftp.mlit

.go.jp/ksj/.

Naya T., Nonogaki S., Komatsubara J., Miyachi Y.,

Nakazawa T., Kazaoka O., … Nakazato H. (2018).

Explanatory text of the Urban Geological Map of the

northern area of Chiba Prefecture, 55p. Tsukuba,

Japan: Geological Survey of Japan, AIST (in

Japanese with English abstract).

Nonogaki S., Masumoto S., & Shiono K. (2012).

Gridding of geological surfaces based on equality-

inequality constraints from elevation data and trend

Fig. 5: Provisional 3D geological model of central Tokyo.

https://fgd.gsi.go.jp/down

https://nlftp.mlit/

42 Susumu Nonogaki and Tsutomu Nakazawa/ Thai Geoscience Journal 2(2), 2021, p. 38-42

data. International Journal of Geoinformatics, 8, 49–

60.

Nonogaki S., Masumoto S., Nemoto T., Nakazawa T., &

Nakayama T. (2020). Voxel modeling of lithofacies

using Voronoi diagram based on locations of a large

number of borehole data. Geoinformatics, 31, 3–10

(in Japanese with English abstract). doi: 10.6010/

geoinformatics.31.1_3

Shiono K., Masumoto S., & Sakamoto M. (1998).

Characterization of 3D distribution of sedimentary

layers and geomapping algorithm—Logical model of

geologic structure. Geoinformatics, 9, 121–134 (in

Japanese with English abstract). doi: 10.6010/geo

informatics1990.9.3_121

Thai Geoscience Journal 2(2), 2021, p. 43-60 43 Copyright © 2021 by the Department of Mineral Resources of Thailand

ISSN-2730-2695; DOI-10.14456/tgj.2021.5

REE and Th potential from placer deposits: a reconnaissance study of

monazite and xenotime from Jerai pluton, Kedah, Malaysia

Fakhruddin Afif Fauzi1*, Arda Anasha Jamil2, Abdul Hadi Abdul Rahman3, Mahat Hj. Sibon3,

Mohamad Sari Hasan4, Muhammad Falah Zahri5, Hamdan Ariffin1, Abdullah Sulaiman1 1Department of Mineral and Geoscience Kedah / Perlis / Pulau Pinang, Alor Setar, Malaysia

2Department of Mineral and Geoscience Johor, Johor Bahru, Malaysia 3Department of Mineral and Geoscience Selangor / W.P., Shah Alam, Malaysia

4Department of Mineral and Geoscience Pahang, Kuantan, Malaysia 5Technical Service Division, Department of Mineral and Geoscience, Ipoh, Malaysia



Abstract

Thorium (Th), rare earth elements (REE), yttrium (Y) and scandium (Sc) are among crucial

elements in minerals that have a very high worldwide demand for green energy generation and

high technology manufacturing industries. The current principal ore minerals for these elements

are monazite, bastnäsite and xenotime. A reconnaissance study on monazite and xenotime

minerals was conducted in southern part of Jerai peak area, which consists of mostly pegmatites

and granite bedrocks and alluvial plains. Heavy mineral concentrate samples were obtained from

various origins including gravelly layer from stream banks, flowing stream beds and seasonal

stream beds for recent fluvial environment. Samples were also taken from weathered bedrocks of

pegmatites and granites and different subsurface profiles from 12 pits dug in the alluvial plain

area. Monazite and xenotime contents from stream bed samples are higher (8.43% and 6.05%)

compared to other origins in recent fluvial environment and higher in weathered pegmatites

(13.70% and 1.45%) compared to weathered granites. The monazite and xenotime content are also

higher in eastern side of the alluvial plain, up to 3.16% and 2.91% respectively, but lower than

samples from recent fluvial environment. The Th, REE and Y contents are very high up to 1,530

ppm, 21,031 ppm and 7,604 ppm respectively in samples containing monazite and/or xenotime.

The Sc content, however, is very low which is up to 87.8 ppm in all samples although it shows

positive correlation with monazite and/or xenotime contents. Both REE containing minerals could

be economically potential if mined as placer suites together with garnet, tourmaline and other

industrially beneficial minerals.

Keywords: Jerai, Kedah, monazite, REE, thorium, xenotime

1. Introduction

1.1 Background

The importance of rare earth elements

(REE), thorium (Th), yttrium (Y) and scandium

(Sc) has become worldwide emergence in

electronics and high technology industries. REE,

Y and Sc are crucial for production of magnets in

computer drives and defence applications, metal

alloys including batteries and superalloys,

phosphors such as LED and optical sensors,

additive in ceramics and glass polishing and also

used as catalyst in various chemical processes

(Jha, 2014). Th, as ThO2 is well-known for better

energy generating purpose than uranium (U) as

the former does not easily oxidized and resistant

to ionic radiation (IAEA, 2005).

REE is defined as a set of 17 chemical

elements in the periodic table, comprising 15

lanthanides which are cerium (Ce), dysprosium

(Dy), erbium (Er), europium (Eu), gadolinium

(Gd), holmium (Ho), lanthanum (La), lutetium

(Lu), neodymium (Nd), praseodymium (Pr),

promethium (Pm), samarium (Sm), terbium

(Tb), thulium (Tm) and ytterbium (Yb), as well

as yttrium (Y) and scandium (Sc) (Connelly

and Damhus, 2005).

The history of REE dated back in 1788

when Johan Gadolin discovered a rare pitch-

-black rock in Ytterby, Sweden. The rock

44 Fakhruddin Afif Fauzi et al. / Thai Geoscience Journal 2(2), 2021, p. 43-60

samples were taken across European countries

where their scientists competed to distinguish

elements that exist as well as to complete the

Lanthanide Series of Periodic Table of

Elements. In fact, the names of yttrium,

erbium, terbium and ytterbium derived from

the origin of the sample. Th, on the other hand,

was discovered by Jöns Jacob Berzelius, a

Swedish scientist in 1828.

Placers are defined as mineral deposits

formed by the mechanical concentration of

minerals from weathered debris, such as beaches

and streams, by which the economic mineral

deposits have high density but are very resistant

to chemical and physical breakdown (Sengupta

and Van Gosen, 2016). Among these minerals

are monazite, xenotime, bastnäsite and loparite

which are considered as the most important

placer rare earth minerals (REM) in the world

(Zhou et al., 2017). The former 2 minerals are

common by-products of alluvial tin mining in

Malay Peninsular since early 1900s (Willbourn,

1925). The placer REM are practically mined

together with other minerals including garnet,

zircon, cassiterite, and Ti-bearing minerals like

rutile and ilmenite as mineral suite or co-products

before separation processes (Sengupta and Van

Gosen, 2016).

Placer REM currently represent the third

most important global REE source of production

after Bayan Obo carbonate rocks in inner

Mongolia and Mountain Pass carbonatites in

California, which come from the monazite and

xenotime dispersed in Neogene to Quaternary

beach sand in Australia (McLennan and Taylor,

2012). In comparison, current and previous

productive placer deposits contain 6% to 7% of

heavy minerals including REM as reported in

Eneabba district, Australia and Xun Jiang

district, China (Shepherd, 1990; Jackson and

Christiansen, 1993).

In 1980s, the xenotime-bearing alluvial

placer deposits in Malaysia were once the

largest source of Y in the world (Castor and

Hendrick, 2006). JMG (2019) stated that the

production of both monazite and xenotime in

Malaysia increased from 25 tonnes in 2009 to

1,654 tonnes in 2018, which were obtained

from alluvial tailings in Ipoh, Perak. USGS

(2019) estimated that Malaysia has 30,000

tonnes of rare earth oxides (REO) in 2018.

Monazite is a phosphate mineral consisting

REE (Ce, La, Nd), Th and U. Monazite is a

common accessory mineral in peraluminous

granites, syenitic and granitic pegmatites, quartz

veins and carbonatites but lesser in charnockites,

migmatites and paragneisses (Rapp and Watson,

1986). In peraluminous granites, monazite

constitutes a major host of LREE, excluding Eu,

Th and U, with minor amount of Y and HREE

(Hinton and Paterson, 1994; Bea et al., 1994;

Bea, 1996). The monazite stability in silicate

melts depends on SiO2, CaO and P2O5, including

oxygen fugacity, peraluminous content and

content ratios of lanthanides and actinides

(Cuney and Friedrich, 1987; Casilas et al., 1995).

Felsic differentiation towards granite plutons

strongly depletes LREE and Th due to monazite

fractionation (Ward et al., 1992; Wark and Miller,

1993; Zhao and Cooper, 1993). According to Che

Zainol Bahri et al. (2018), the Th content in

Malaysian monazite ranges between 2,525 ppm

to 40,868 ppm while Willbourn (1925) mentioned

that the mineral contains 3.5% to 8.38% of

ThO2. Atomic Energy Licencing Act 1984 stated

that if radionuclide of Naturally Occurring

Radioactive Materials (NORM) of Th-232

exceeds 1 Bq/g, it is considered as radioactive.

1 Bq/g of Th-232 is equivalent to 246 ppm,

assuming the chain is in equilibrium.

Xenotime is also a phosphate mineral but

abundant particularly in Ca-poor peraluminous

granites, which accounts for huge fraction of Y

and HREE contents and variable portion of

substituted U (Wark and Miller, 1993; Bea,

1996). In xenotime-bearing peraluminous gra-

-nites, the Y and HREE fractions contained in

xenotime vary from 30% to 50%, that is closely

related to xenotime-apatite-zircon concomitance

during plutonic facies differentiation (Bea, 1996;

Wark and Miller, 1993; Förster and Tischendorf,

1994). Xenotime also contains minor amounts

of Th and LREE, particularly Nd and Sm

(Förster, 1998b).

Hence, this conducted study is to determine

the potential of Th and REE based on monazite

and xenotime distributions in placer environments

within Jerai Pluton area.

Fakhruddin Afif Fauzi et al. / Thai Geoscience Journal 2(2), 2021, p. 43-60 45

1.2 Previous studies

Studies on the occurrences of monazite and

xenotime in Malaysia were commenced as parts

of regional mapping and regional geochemical

surveys by Geological Survey of Malaysia since

1925, continued by Department of Mineral and

Geoscience Malaysia (JMG) from 2000 until

present.

The Malaysian monazite generally has

moderately well-rounded discrete or as some

parts with colour varies from clear, deep canary

yellow through cream coloured with resinous

lustre due to progressive oxidation of REE

(Flinter et al., 1963; Wan Hassan, 1989). The

Jerai monazite, however, has unusual elongated

rolled grains of flattened form with deep green

colour (Wan Hassan, 1989; Flinter et al., 1963).

Wan Hassan (1989) distinguished the xenotime

crystal habit to have squat tetragonal bipyramid

in Malaysian Tin Belt and prism with double

pyramidal terminations in Malaysian Eastern

Belt.

Studies on radioactive minerals on Malaysian

Central Belt then were conducted in 1993 to

1995 (Mohd Hasan et al. 1993, 1995; Zakaria et

al. 1994). Academy of Sciences Malaysia

(ASM) later initiated a study on REE associated

with ion adsorption clay in 2013 (ASM, 2014).

In 2018, JMG conducted a reconnaissance

study on REE, Th and Sc potentials in Malaysia.

The preliminary study comprised their potential

in clayey horizons in weathered granites and

placer deposits, including Jerai Pluton (Abdul

Rahman et al. 2018a, b). Hence, this paper is

aimed to deliver the outcomes of the study

commenced in the pluton area.

1.3 Study area

The study area is situated at the south of

Mount Jerai, west of Kedah state with a total of

40 km2. The area is mostly covered with paddy

fields with freshwater for drainage sourced

from streams flowing from the peak. The study

area lies in the National Jerai Geopark (Fig.1).

2. Geological Setting

2.1 Regional geology

The Jerai Pluton lies within the western tin

granites of Peninsular which is part of the

Southeast Asian Magmatic Arc that was

triggered during Late Permian to Triassic

subduction-collision event due to the closure of

Palaeo-Tethyan Ocean beneath the Southeast

Asian crust (Robb, 2019) (Fig.1).

The tin granites of western Peninsular

Malaysia have been considered as products of

partial melting of the metamorphic basement

during the collision of Sibumasu and East

Malaya blocks (Liu et al., 2020; Ng et al., 2015),

based on their ilmenite-series, peraluminous

character (Ishihara et al., 1979), and charac-

teristic of S-type granites (Chappell and White,

2001). More recently, the genetic link between

the tin mineralization and the granites has been

constrained, by which the age of tin ores and their

granitic hosted rocks in the western Peninsular

Malaysia is within the range of the 230 to 210 Ma

(Yang et al., 2020).

2.2 Local geology

The study area consists of granitic bedrock,

metasedimentary bedrocks and unconsolidated

deposits.

The granitic bedrock covered the northern

part of the study area. It is from the Jerai Pluton

that intruded during Late Triassic and shaped the

mountain (Fig.1). Jamil et al. (2006) divided the

pluton into 3 facies according to mineralogical

criteria, which are biotite – muscovite granite,

tourmaline granite and pegmatite. The pegmatite

facies which occurred as veins ranging from few

centimetres to several meters, are the primary

source of tin associated with Nb-Ta (Bradford,

1972). Khoo (1977) proposed that the pegmatites

also occurred as sync-plutonic dykes that filled

the ductile cracks in granites during intrusion.

Apart of tourmalines, garnets, particularly pinkish

variety, are the common accessory minerals in

Jerai Granite found in this study.

The metasedimentary facies within the

study area are quartzites and schists from

Cambrian Jerai Formation. Both facies are

mineralized with magnetite and/or hematite

(Bean and Hill, 1969; Bradford, 1972) and

regarded as source of iron ores since 535 B.C.

(Mokhtar and Saidin, 2018).


Fig. 1: Maps showing the Granite Belts and tin belts in Peninsular Malaysia (above, after Hosking, 1973) and

the general geology of study area (below, after JMG, 2014).


The unconsolidated deposits cover the southern

part of the study area. They mostly consist of

clay, mud and silt originated from marine

influence during Quaternary period (JMG,

2014).

3. Materials and Methodology

Heavy concentrate samples were collected

from current and seasonal stream beds, stream

banks and gravelly layers on stream banks;

weathered granites and pegmatites (Figs. 1, 2,

3, 4 & 5) and distinguishable layers from dug

pits with depth between 3.2 metres up to 4.0

metres (Figs. 6 & 7) All sampling locations are

shown in Fig. 8.

The samples were obtained through panning

using 5 litre sized wooden pan. All samples then

underwent removal of light minerals (i.e. SG ≤

2.85) including quartz using Bromoform

solution before thoroughly rinsed with spirit

methyl, followed by distilled water. Once dried,

the samples were weighted and magnetically

separated using hand magnet and Frantz

Isodynamic Magnetic Separator Model L-1 into

4 different magnetism; 0.4 Ampere, 0.7 Ampere,

1.0 Ampere and non-magnetic.

Samples of different magnetism were then

taken for quantitative mineral estimation

(QME) analysis under stereo microscope aided

by mineral lists according to magnetism (Table

1) and descriptions by Wan Hassan (1989) and

Devismes (1978).

Selected concentrate samples were analysed

through LA-ICP-MS method in Laboratory

Branch, JMG Technical Service Division in

order to determine their REE, Th, Y and Sc

contents. The U content is also analysed for all

selected samples. Apart from individual content,

the REE results are also calculated according to

total light REE (TLREE), total heavy REE

(THREE) and total REE (TREE).

4. Results

A total of 43 samples including 3 samples

from weathered bedrocks and 28 samples from

pits were successfully obtained in this study.

4.1 QME analysis

The monazite content in samples from recent

fluvial environment (Table 2) is from none to

8.43% and the xenotime content in samples from

the same environment is from none to 6.05%.

Sample KC56 which originated from stream bed

contains the most monazite and xenotime.

Samples KC41 and KC59 also contain monazite

more than 4% and sample KC41 has xenotime

content more than 4%. Garnet, particularly

pinkish variety is common in all samples while

allanite and zircon exist in few samples. Other

minerals identified include mostly magnetite,

hematite and tourmaline (Figs. 9 & 10). The

average content of monazite and xenotime in

recent fluvial environment samples is 5.14% and

2.82% respectively, with an average sum of

7.96%.

While for weathered bedrock samples, the

highest monazite and xenotime content is in

pegmatite, which is 13.70% and 1.45% respec-

tively, compared to weathered granite.

In general, sandy layers in pits have

considerably greater amount of heavy concen-

trate minerals compared to silty and clayey

layers. The monazite and xenotime content in

samples from pits (Table 3) is ranging from none

to 3.16% and none to 2.91%, respectively. The

highest content of both monazite and xenotime

originated from pit C but in different layers, by

which the deeper layer (KCC003) has higher

content of monazite 3.16% while shallower layer

(KCC001) has greater content of xenotime

(3.91%). Similar to samples from recent fluvial

environments, pinkish garnet is also common in

all samples while allanite and zircon appear in

few samples. Other minerals identified are

magnetite, hematite, tourmaline and ilmenite. No

mineral concentrates exist from upper layer of pit

I (KIC001) and pit K as these pits mainly consist

of greyish mud – clay with organic materials. The

average content of monazite and xenotime in

Quaternary deposit environment samples is only

1.66% and 1.10% respectively, with an average

sum of 2.76%.

4.2 LA-ICP-MS analysis

A total of 10 concentrate samples from

recent fluvial environment were analysed by

LA-ICP-MS (Table 4). The Th content of the


A

B

Fig. 2: Origins of the samples in recent fluvial environment

include gravelly layer (A) and stream bed (B).

Fig. 3: The occurrence of eluvial bed

near S. Batu Pahat.

Fig. 4: Sampling of weathered bedrock.

Fig. 5: Outcrops of weathered granite and pegmatite bedrocks from Jerai Pluton in contact with quartzite of

Jerai Formation.

Fig. 6: Pit is dug using JCB excavator. Fig. 7: One of the dug pits.


samples ranges from 74.6 ppm to 1,530.0 ppm.

The U content ranges from 48.5 ppm to 1,553.0

ppm. The Sc content ranges from 16.5 ppm to

87.8 ppm while the Y content ranges from

266.0 ppm to 7,604.0 ppm.

The TREE content ranges from 928 ppm

to21,031 ppm. The THREE content ranges from

411 ppm to 11,435 while ther TLREE content

ranges from 517 ppm to 9,596 ppm All samples

have higher TLREE than THREE content

except KC56 and KC59.

Sample KC56 has the highest content of U,

Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb

and Lu and also TREE, HREE and LREE.

Sample KC41 has the greatest content of Th

and Ce while sample KC59 has the greatest

content of Sc. Sample KC23 has the lowest

content of Th, U, Y, TREE, THREE and

TLREE.

4.3 Statistical relationships

Comparisons of QME and LA-ICP-MS

Fig. 8: Sampling locations in the study area.


Table 1: List of common minerals separated using Bromoform, hand magnet and magnetic

separator according to magnetism (Che Harun et al. 2009).

results are presented as crossplots of selected

elements and minerals in Fig. 11. They show

no perfect linear relationship (R2 > 0.95)

between the element and mineral content.

However, Th and REE have generally strong,

positive relationship with monazite. Similar

positive histogram patterns for Ce-Nd-La vs

monazite are observed. The Sm vs monazite

histogram pattern is similar to the REE vs

monazite histogram pattern.

The Y element has strong, positive relation-

ship with both monazite and xenotime. Similar

pattern of Y vs xenotime histogram is shown by

the Yb vs xenotime histogram.

The Sc element, however, has better positive

relationship with monazite compared to garnet

while U has strong relationship with monazite.

5. Discussions

5.1 Monazite and xenotime magnetism

In this study, the Jerai monazite is not only

observed in 0.7-Amp fraction but also appeared

but less in 1.0-Amp fraction. This is acceptable

as monazite mineral is always slightly magne-

-tised compared to quartz but very much weaker

than hematite (Willbourn, 1925; Abaka-Wood

et al., 2016).

The xenotime mineral observed in both 0.4-

and 0.7-Amp fractions are in concordance with

the mineral magnetism guide (Table 1) and the

fact that it has slightly higher magnetism than

ilmenites (Kim and Jeong, 2019).

5.2 Monazite and xenotime distribution

The higher content of monazite and xenotime

in weathered pegmatite compared to weathered

granites indicates that pegmatite facies in Jerai

Pluton is the primary source of both rare earth

minerals.

The humid, tropical climate with high

precipitation allows granitic bedrock to decom-

pose to kaolinite and lateritic soils. This permits

highly resistant minerals including monazite and

xenotime to be transported and deposited either

into eluvial environments and nearby river

systems before reaching alluvial plain further

downstream to become placer deposits (Ghani et

al., 2019). The occurrences of pegmatites close

or at the upstream of sampling points in recent

fluvial environment could be the main factor of

different content of the minerals regardless of

the sample origin. This is shown by the fact that

samples KC56 and KC41, which were taken

from stream bed and alluvial bed respectively,

have relatively higher monazite and xenotime

contents as both sampling points are in the

same S. Batu Pahat basin while pegmatite

Light minerals

(separated with

Bromoform)

Magnetic

(hand magnet)

Magnetic Separator (Frantz Isodynamic Model L-1

0.4

Ampere 0.7 Ampere 1.0 Ampere

Non-

Magnetic

Quartz Magnetite

Hematite

Iron Oxide

Pyrrhotite

Ilmenite

Iron Oxide

Garnet

Siderite

Ilmenite

Tourmaline

Staurolite

Pyrite

Epidote

Garnet

Hydroilmenite

Xenotime

Seiderite

Allanite

Columbite

Rutile

Wolframite

Tourmaline

Hydroilmenite

Monazite

Pyrite

Quartz

Epidote

Staurolite

Allanite

Columbite

Garnet

Xenotime

Rutile

Struverite

Pyrite

Quartz

Cassiterite

Rutile

Leucoxene

Corundum

Tourmaline

Topaz

Zircon

Gold

Anatase


Table 2: Mineral contents (%) in samples obtained from recent fluvial environment. The symbol ‘-‘ denotes not detected and ‘TR’ denotes trace.

Sample No. K023 KC30 KC32 KC36 KC40 KC41 KC54 KC56 KC59 KC57 KC63 KC64

Origin Gravelly

layer

Seasonal

stream

Gravelly

layer

Gravelly

layer

Alluvial

bed

Alluvial

bed

Stream

bed

Stream

bed

Eluvial

bed

Weathered

pegmatite

Weathered

pegmatite

Weathered

granite

Allanite TR TR TR - - - 1.38 - - - - -

Garnet 32.52 6.18 25.25 39.37 23.75 6.83 47.59 40.56 17.06 0.76 5.61 0.06

Monazite TR 3.30 - 0.96 - 4.34 0.81 8.43 4.82 4.72 13.70 -

Xenotime - 3.10 - TR TR 4.41 TR 6.05 1.76 0.17 1.45 TR

Zircon - 4.59 0.27 - - 0.72 TR - 0.33 - 0.31 TR

Other Minerals 67.48 82.82 74.49 59.67 76.25 83.69 50.22 44.97 76.02 94.36 78.93 99.94

Total Weight

Analyzed (g)

4.53 5.66 2.83 2.76 2.92 2.21 2.53 2.87 2.55 2.11 2.89 2.34

Table 3: Mineral contents (%) in samples obtained from Quaternary alluvial environment. The symbol ‘-‘ denotes not detected and ‘TR’ denotes trace.

Pit A B C D

Sample No. KAC

001

KAC

002

KAC

003

KBC

002

KBC

003

KBC

004

KBC

005

KCC

001

KCC

002

KCC

003

KDC

001

KDC

002

KDC

003

Depth (m) 1.2 – 2.1 2.1 – 2.8 2.8 – 3.6 0.4 – 1.0 1.0 – 1.8 1.8 – 2.8 2.8 – 3.6 0.5 – 0.6 1.2 – 2.3 2.7 – 2.7 0.7 – 1.2 1.2 – 2.4 2.5 – 3.4

Allanite - - 0.63 TR - - - - - - - - -

Garnet 7.08 5.34 8.61 11.01 7.64 4.85 8.63 61.28 52.14 59.28 4.05 11.57 4.39

Monazite - 1.35 - TR - TR TR 1.47 TR 3.16 - - TR

Xenotime - - - - TR - - 2.91 - 0.79 TR TR 0.83

Zircon 2.67 0.22 1.42 TR 0.27 0.13 - TR 0.42 - 0.24 - 0.33

Other Minerals 90.25 93.10 89.34 88.99 92.09 95.02 91.37 34.33 47.44 36.78 95.71 88.43 94.45

Total Weight

Analysed (g)

3.05 2.97 3.02 2.98 2.75 2.97 3.06 2.78 2.85 3.04 2.96 3.72 3.01


Table 3 (cont.): Mineral contents (%) in samples obtained from Quaternary alluvial environment. The symbol ‘-‘ denotes not detected and ‘TR’

denotes trace.

Pit E F G H I

Sample No. KEC

001

KEC

002

KEC

003

KFC

001

KFC

002

KGC

001

KGC

002

KHC

001

KHC

002

KHC

003

KIC

001

KIC

002

Depth (m) 0.7 – 1.6 1.7 – 2.4 2.5 – 3.2 1.0 – 1.2 2.7 – 3.2 0.6 – 1.6 1.6 – 3.2 0.6 – 1.0 3.0 – 3.2 3.2 – 3.7 1.6 – 2.5 2.8 – 3.6

Allanite - - - - - - - - - -

(no

con

cen

trat

e ex

ists

) -

Garnet 3.25 1.36 3.79 9.90 3.09 5.95 9.20 6.00 2.20 6.20 10.08

Monazite TR - 0.75 TR 1.62 TR TR TR - - TR

Xenotime 1.54 TR 0.75 0.00 TR - - 1.14 - - 0.86

Zircon 0.32 0.36 - - - - 0.71 - 0.43 TR 0.65

Other Minerals 94.88 98.28 94.71 90.10 95.29 94.05 90.08 92.86 97.36 93.80 88.40

Total Weight

Analysed (g)

2.95 2.64 3.06 3.09 3.11 2.69 3.08 2.80 2.54 3.03 2.38

Table 3 (cont.): Mineral contents (%) in samples obtained from Quaternary alluvial environment. The symbol ‘-‘ denotes not detected and ‘TR’ denotes

trace.

Pit J K L

Sample No. KJC

001

KJC

002

KKC

001

KKC

002

KLC

001

KLC

002

Depth (m) 0.7 – 2.1 3.1 – 3.6

(no

con

cen

trat

e o

bta

ined

)

(no

con

cen

trat

e o

bta

ind

e) 0.7 – 2.0 2.0 – 3.3

Allanite - - - -

Garnet 5.97 9.90 5.76 1.06

Monazite TR TR 1.61 TR

Xenotime - - TR TR

Zircon 0.51 - 0.64 0.15

Other Minerals 93.52 90.10 92.00 98.80

Total Weight

Analysed (g)

2.84 3.09 2.18 3.03


XENOTIME GARNET MONOZITE TOURMALINE

Fig. 9: Minerals observed in 0.7 Amp sample fraction of KC56 under stereo microscope. Total magnification is

40x.

GARNET MONOZITE TOURMALINE

Fig. 10: Minerals observed in 1.0 Amp sample fraction of KCC003 under stereo microscope.

Total magnification is 35x.


Table 4: Th, U, Sc, Y and REE content (in ppm) in selected concentrate samples.

Sample

No. Th U Sc Y

LREE HREE TREE

+Y

THREE

+Y TLREE

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

KC23 74.6 48.5 22.5 266.0 114.0 255.0 25.6 98.8 23.6 0.3 20.5 4.6 32.9 6.9 23.3 5.2 44.4 7.2 928.4 411.0 517.3

KC30 198.0 255.0 35.2 750.0 312.0 752.0 83.7 297.0 94.1 0.2 81.4 18.1 107.0 19.5 60.0 12.5 102.0 16.5 2706.0 1167.0 1539.0

KC32 210.0 272.0 44.2 1088.0 317.0 750.0 82.0 301.0 97.6 0.8 96.4 23.3 149.0 27.8 83.5 17.8 145.0 23.0 3202.2 1653.8 1548.4

KC36 319.0 201.0 35.7 825.0 441.0 1013.0 112.0 395.0 104.0 2.0 88.1 18.0 112.0 21.8 66.7 13.5 110.0 17.3 3339.5 1272.4 2067.1

KC40 168.0 104.0 16.5 372.0 249.0 565.0 58.9 207.0 47.2 1.0 37.7 7.6 49.3 9.8 30.4 6.2 49.4 7.6 1698.0 569.9 1128.1

KC41 1530.0 639.0 48.9 3650.0 1979.0 4537.0 494.0 1769.0 438.0 10.8 390.0 77.6 482.0 94.8 288.0 55.6 405.0 61.5 14732.3 5504.5 9227.8

KC54 252.0 290.0 48.2 951.0 405.0 905.0 101.0 359.0 99.0 1.9 89.3 20.2 129.0 24.7 76.1 16.5 133.0 20.7 3331.4 1460.5 1870.9

KC56 1383.0 1553.0 70.1 7604.0 2011.0 4531.0 529.0 1911.0 608.0 6.3 644.0 154.0 1014.0 196.0 590.0 124.0 962.0 147.0 21031.3 11435.0 9596.3

KC57 312.0 414.0 36.4 1546.0 497.0 1174.0 133.0 472.0 156.0 0.4 154.0 35.1 221.0 40.3 121.0 24.9 203.0 31.4 4809.1 2376.7 2432.4

KC59 704.0 1097.0 87.8 5214.0 1071.0 2550.0 300.0 1077.0 390.0 1.7 445.0 110.0 717.0 135.0 402.0 85.7 684.0 107.0 13289.4 7899.7 5389.7

Min. 74.6 48.5 16.5 266.0 114.0 255.0 25.6 98.8 23.6 0.2 20.5 4.6 32.9 6.9 23.3 5.2 44.4 7.2 928.4 411.0 517.3

Max. 1530.0 1553.0 87.8 7604.0 2011.0 4537.0 529.0 1911.0 608.0 10.8 644.0 154.0 1014.0 196.0 590.0 124.0 962.0 147.0 21031.3 11435.0 9596.3

Ave. 515.1 487.4 47.7 2226.6 739.6 1703.2 191.9 688.7 205.8 2.5 204.6 46.9 301.3 57.7 174.1 36.2 283.8 43.9 6906.8 3375.1 3531.7


a)

b)

c)

d)

e)

f)

g)

h)

i)

j)

k)

l)

Fig. 11: Plots of selected elements vs minerals with goodness-of-fit values (R2).


dykes occurred at the upstream of the river

basin (Bradford, 1972). Sample KC30 which

also contains considerable amount of monazite

and xenotime could have pegmatite bedrock at

upstream while sample KC54, although

collected from stream bed of S.Ayer Jerneh,

contains only traces of both minerals. This is

due to fact that pegmatites do not occur much

at its upstream (Bradford, 1972).

The gravelly layers at recent stream banks

are regarded as the paleo stream beds of high

energy water flow (Harraz, 2013). However,

very low monazite and xenotime content in the

layers is either due to dispersion of the minerals

during deposition by high energy stream flow

or the parent rocks did not completely weather

yet to permit both minerals to deposit. In the

alluvial plain, the lower content of monazite

and xenotime than in the recent fluvial

environment is expected as heavy minerals,

including both rare earth minerals were

widespread when reaching the relatively flat

plain area under lower energy regime (Gupta

and Krishnamurthy, 2005).

In comparison, the monazite and xenotime

contents between sampling points in the

alluvial plains show relatively higher at eastern

side (downstream S. Batu Pahat) compared to

western side (downstream S. Jerneh and S.

Badong). The main factor of different

distribution pattern is the influence of marine

sedimentation during Pleistocene period at the

western plain area (Khoo, 1996; Allen, 2000).

This is also supported by the occurrence of

clayey or muddy layers in pits in that area,

suggestive of Gula Formation which were

deposited in paleo tidal flat or swamp

environment during following Holocene period

(Hassan, 1990) (Fig. 12).

5.3 Elements and mineral relationships

A positive relationship is shown by Th and

monazite, indicating that monazite is the chief

mineral containing the radioactive element. This

is also shown by strong relationship between U

and monazite. Monazite is one of the minerals

searched for its Th content, although the Th

content is lower than in thorianite (ThO2) and

thorite ((Th,U)SiO4) (Voncken, 2016). The U

occurs as U4+ only as accessory in selected

minerals like apatite, zircon and monazite that is

concentrated into residual melts (Robb, 2005).

However, thorianite, thorite and apatite are not

observed during QME analysis while zircon

occurs in very lesser amount compared to

monazite but low Th and U content may also be

contributed by dark Nb-Ta minerals that could

exist in placer deposits (Bradford, 1972; Zhang

et al., 2002).

Apart from radioactive elements, the

monazite also has strong relationships with REE,

Y and Sc, indicating that the Jerai monazite

contains many elements in its crystal lattices.

Monazite generally contains higher amount of

HREE while xenotime tends to contain higher

amount of LREE (Förster, 1998a, b). All samples

in this study, excluding KC41, KC564 and

KC57, fit the different LREE-HREE concen-

trations.

The similarities of La, Ce and Nd vs monazite

plots could represent uniform concentration ratios

of these element in one monazite mineral. In fact,

the highest content of Ce compared to La and Nd

would suggest the monazite-Ce species occurs the

most in Jerai area (Mindat.org, 2021).

The Y content has stronger relationship with

monazite compared to xenotime. Although Y is

the main element in xenotime, Flinter et al.

(1963) studied that the Jerai monazite also

contains considerably high amount of Y with

value ranges 2.5% to 5.9%. The variation of Y

content could also be the main factor of samples

containing higher monazite than xenotime, but

has higher HREE concentration because Y is

considered as HREE in this study.

Similarities of Y and Yb plots are due to

fact that both HREE also have uniform

concentration ratios and tend to occur together

(Förster, 1998b).

Sc is likely contributed by monazite

compared to garnet, although its content is

considerably very low. Sc is more common as

trace amounts in iron and magnesium rich

rocks (Gupta and Krishnamurthy, 2005).

5.4 Mining potential

The maximum total content of monazite and


xenotime per sample is 14.48% in stream bed of

S. Batu Pahat (KC56) for recent fluvial

environment and 4.38% in Quaternary alluvial

plain environment KCC001 (KCC001). These

contents are exceptionally higher than those in

productive placer deposits in Eneabba (Australia)

and Xun Jiang (China) districts (Shepherd,

1990; Jackson and Christiansen, 1993). In

comparison of sum average of both minerals,

fluvial deposit has relatively more potential.

Rather than mining the REM alone,

exploiting all existing heavy mineral suits could

be more potential yet economic to practice.

Garnets are the most occurring minerals in all

samples for both fluvial and alluvial

environments. Garnets are used to make

abrasives to clean compacted mud and silt from

well casings in petroleum industry and to

polish optical lenses and metal (Rock&Gem,

2019). Tourmaline, particularly black, schorl

species are also abundant in all samples. It is

widely used based on its pyroelectricity and

emission of far infrared radiation (Lameiras et

al., 2010). Other minerals that exist abundantly

in placer deposits in Jerai area include

hematite, magnetite, Nb-Ta minerals and lesser

cassiterite (Bradford, 1972) still has industrial

demands.

Fig. 12: Simplified geological map showing the studied pithole locations with respect to Kedah Bay and Merbok

Estuary area and coastal line before 15th Century (modified from Khoo, 1996). The sea level may be higher

during that time according to the discovery of ancient jetty near Sungai Batu Archaeological Site (Zakaria et al.,

2011).


6. Conclusion and recommendation

The monazite and xenotime contents are

relatively higher in recent fluvial deposits than

Quaternary alluvial deposits. Higher content of

both minerals was shown in both fluvial and

downstream, alluvial plains of S. Batu Pahat

basin. The occurrences of pegmatite as chief

host rock for monazite and xenotime at

upstream could be the factor of higher content

of the minerals in S. Batu Pahat than S. Ayer

Jerneh and S. Singkir. The lower content of

mineral samples including monazite and

xenotime in western side of Quaternary plain is

due to influence of marine sedimentation

during Quaternary period. The higher Th and

LREE content are contributed by monazite

while Y and HREE are chiefly contributed by

xenotime. The Sc content is also contributed by

monazite although it is considerably low.

The monazite and xenotime in Jerai area

are economically potential as placer deposits if

mining method considers of harvesting other

minerals like garnet, tourmaline, iron ores and

Nb-Ta minerals which could be industrially

beneficial. Other analysis techniques such as

XRD, FESEM and EPMA are also recom-

mended to be done in order to detail the mineral

contents in the placer deposits.

Acknowledgements

The authors would like to thank The

Director General of JMG Malaysia for giving

the opportunity for this study to be published

and JMG REE Team for ideas and supports

given during this study. Also special thanks to

Ms. Brendawati Ismail, JMG Chief Editor and

Mr. Ledyhernando Taniou for proofread.

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Thai Geoscience Journal 2(2), 2021, p. 61-71 61


ISSN-2730-2695; DOI-10.14456/tgj.2021.6

Geology, occurrence and gemmology of Khamti amber

from Sagaing region, Myanmar

Thet Tin Nyunt1*, Cho Cho2, Naing Bo Bo Kyaw3, Murali Krishnaswamy4,

Loke Hui Ying5, Tay Thye Sun5, Chutimun Chanmuang N6.

1 Department of Geological Survey and Mineral Exploration, Ministry of Natural Resources and Environmental

Conservation, 15011 Nay Pyi Taw, Myanmar 2 School of Earth Sciences, China University of Geosciences (Wuhan); Myanma Gems Enterprise, 15011

Nay Pyi Taw, Myanmar 3 Myanma Gems Enterprise, 15011 Nay Pyi Taw, Myanmar

4 Department of Chemistry, NUS High School of Mathematics and Science, 20 Clementi Ave. 1, Singapore 129957 5 Far East Gemological Laboratory, 12 Arumugam Road #04-02, LTC Building B, Singapore 409958

6 Institut für Mineralogie und Kristallographie, Universität Wien, Althanstraße 14, 1090, Vienna, Austria


Received 17 March 2021; Accepted 4 June 2021

Abstract

A large quantity of Burmite (or Myanmar amber) is produced at Tanai in the Hukaung valley in

Kachin State and at Hti Lin (Tilin) in the Magway Region. Another occurrence of amber is found

in Pat-tar bum (also called Pat-ta bum) which is located near the Nampilin stream, about 40 km

southeast of Khamti (Hkamti), Khamti Township, Sagaing Region. The present mining sites in

Pat-ta bum are Laychun (Lachun) Maw (most productive), Kyat Maw, Shan Maw, Gyar Maw,

Kyauk Tan Maw and Nameindra Maw. Low grade metamorphic rocks, Kanpetlet schists and

similar schists to the Naga Hills are exposed in the eastern part which include glaucophane schist,

graphite schist, and epidote schist. Sedimentary units of Miocene age of the Upper Pegu Group

are widely exposed in the western, middle and northeastern part. Amber is found in Orbitolina

(mid-Cretaceous) bearing limestone which ranges from a few centimetres to up to two metres in

thickness. This limestone is intercalated with sandstone and carbonaceous shaley limestone and

sometimes together with carbonaceous materials. The bedding dips vary from 20˚ to 35˚ and

amber production follows the bedding plane. Amber is also found in sandstone and carbonaceous

shale. The primary amber mining is carried out by blasting the amber-bearing limestone,

sandstone and carbonaceous shaley limestone along their bedding planes and aditing. The colour

of Pat-tar bum (Khamti) amber varies from yellow, greenish-yellow, orangy-yellow, golden

yellow, brownish-yellow and brown. Gemmologically, it is transparent to opaque and the

refractive index ranges from 1.53 to 1.54 (spot reading), and the specific gravity ranges from 1.03

to 1.09. Ultraviolet radiation analyses show that very strong chalky yellowish-blue under long

wave and weak chalky yellowish-blue or greenish weak chalky yellowish-blue or greenish under

short wave. Some of the deep brownish material displays weak chalky blue or yellow under long

wave ultraviolet light and inert under short wave ultraviolet light. Inclusions that identified in

amber samples in the present study are flattened gas bubbles, flow marks, some brownish organic

debris and various organic inclusions (spiders, flies, feather-like and plant-like inclusions and

other organic materials). Eleven analysed specimens of Pat-tar bum amber were quite similar to

one another and the IR features are dominated by a group of absorption bands at around 2800–

3000 cm–1, relatively narrow bands in the range of 950–1750 cm–1 overlaying a broad hump at

800–1400 cm–1, and a weak broad band at around 3420 cm–1. Pat-tar bum amber does not show

the characteristic IR and Raman bands of young copal (which lie in the 1050–1250 cm–1 region

and at 1764 cm–1), which provides the confirmation for the older age of the amber i.e., mid-

-Cretaceous as confirmed by Orbitolina sp. in the host limestone.

Keywords: amber, FTIR and Raman spectra, Khamti, Orbitolina sp., Pat-tar bum


62 Thet Tin Nyunt et al. / Thai Geoscience Journal 2(2), 2021, p. 61-71

1. Introduction

Major production of Burmite (Myanmar

amber) in Myanmar is from Tanai, Hukaung

valley in Kachin State and Hti Lin (Tilin),

Magway Region. Another occurrence of amber

is found in Pat-tar bum (also called Pat-ta bum)

which is located near the Nampilin stream,

about 40 km southeast of Khamti (Hkamti),

Khamti Township, Sagaing Region and about

112 km southwest of Tanai (Fig. 1). The

present mining sites in Pat-tar bum are

Laychun (also spelled Lachun or Lachon) Maw

(most productive), Kyat Maw, Shan Maw,

Gyar Maw, Kyauk Tan Maw and Nameindra

Maw (“Maw” means “mine” in Myanmar)

(Thet Tin Nyunt et al., 2019, 2020).

2. Geology

Paleocene to Eocene molasse-type sedimen-

tary units of the Paunggyi Formation and the

Cretaceous units are locally exposed including

limestone in the study area (Fig. 2). Ultramafic

and mafic intrusions of mostly Jurassic age also

occurred (Soe Thura Tun et al., 2014). These

intrusions include peridotite and serpentinite

which are the important source for jadeitite near

Nansibon (Cho Cho, 2016 ; Kyu Kyu Thin, 2016).

Low grade metamorphic rocks, Kanpetlet schists

and similar schists to those of the Naga Hills are

exposed in the eastern part which include

glaucophane schist, graphite schist, and epidote

schist. Orbitolina sp. bearing limestone (mid-

-Cretaceous, Albian?) intercalated with sandstone,

shaley limestone and carbonaceous limestones are

exposed in the Pat-tar bum area. Sedimentary

units of Upper Pegu Group of Miocene age are

widely exposed in the western, middle and

northeastern part.

3. Occurrence of Amber

Amber from Pat-tar bum is found in

Orbitolina sp. (mid-Cretaceous, Albian?) bear-

ing limestone (Fig. 3). The fossils that present

in the amber bearing limestone can only

identify that these fossils ranges from Lower

Aptian to Albian. So more thin sections are

necessary for further identification of this

important fossils (Tian Jiang, pers. comm.).

The thickness of amber bearing limestone is

ranges from a few centimetres to up to two

metres. This lime-stone are intercalated with

sandstone and carbonaceous shaley limestone

and sometimes together with carbonaceous

materials (Thet Tin Nyunt, et al., 2019, 2020).

Fig 1: Location map of the Pat-tar bum amber mine in Sagaing Region.

Thet Tin Nyunt et al. / Thai Geoscience Journal 2(2), 2021, p. 61-71 63

4. Amber Production

Five major production sites including 13

blocks where the mining operation has been

operated by Sea-Sun-Star Co. Ltd. are:

Laychun (Lachun) Maw, Kyat Maw, Shan

Maw, Gyar Maw and Kyauk Tan Maw (Fig. 4).

Nameindra Maw is now under suspension.

Among them, the Laychun Maw is currently

the most productive. The dips of the bedding

vary from 20˚ to 35˚ and amber production is

carried out along the bedding plane by adits.

The primary amber mining is carried out by

blasting the amber-bearing limestone, sand-

stone and carbonaceous shaley limestone along

their bedding plane and aditing into the

limestone. Excavated amber-bearing limestone

were sorted by manpower outside of the adit

(Figs. 5, 6 & 7).

5. Gemmology

The colour of Pat-tar bum (Khamti) amber

varies from yellow, greenish-yellow, orangy-

yellow, golden yellow, brownish-yellow, brown

and reddish brown (Fig. 8). Clarity is from

transparent to opaque, the refractive index ranges

from 1.53 to 1.54 (spot reading), and specific

gravity (SG) ranges from 1.03 to 1.09. These

ranges are typical of amber (O’Donoghue, 2008)

where the higher SG is due to the attachment of

calcite matrix. Ultraviolet radiation analyses show

that very strong chalky yellowish-blue under long

wave and weak chalky yellowish-blue or greenish

Fig 2: Regional geological map of the Pat-tar bum area (after Soe Thura Tun et al., 2014).

Fig 3: Orbitolina sp. in amber bearing mid-Cretaceous (Albian?) limestone (10×, cross-polarised transmitted

light). (photos by Cho Cho)

1 mm


Fig 4: Location map of the Pat-tar bum amber mines.


weak chalky yellowish-blue or greenish under

short wave (Kocsis et al., 2020). Some of the deep

brownish material displays weak chalky blue or

yellow under long wave ultraviolet light and inert

under short wave ultraviolet light.

6. Inclusions in Amber

Inclusions that are contained in amber

samples collected the present study are flattened

gas bubbles, flow marks, some brownish organic

debris and various animal inclusions (spiders,

flies, feathers-like and plant-like inclusions, and

organic materials) (Figs. 9 & 10).

7. FTIR and Raman analyses

In the present study, eleven samples of Pat-

-tar bum amber were analyses by FTIR (Fourier-

-transform infrared) and Raman analyses. Fig. 11

presents a pair of infrared absorption [recorded in

ATR (attenuated total reflection) mode] and Raman spectra obtained from amber sample KT21,

which is representative of all samples analysed

herein. The IR spectrum is dominated by a

group of absorption bands at around 2800–3000

cm–1, relatively narrow bands in the range 950–

1750 cm–1 overlaying a broad hump at 800–

1400 cm–1, and a weak broad band at around

3420 cm–1 (Fig. 11, top; for details see Thet Tin

Nyunt et al., 2020). The positions and relative

intensities of bands in the IR spectrum of

Khamti amber are similar to those seen in the IR

spectra of Myanmar amber from Tanai and Hti

Lin regions reported by various authors (e.g.

Tay et al., 2015; Liu, 2018; Chen et al., 2019;

Jiang et al., 2020; see Fig. 12), with the

exception of a broad band at around 3420 cm-1

(present study) or 3500 cm–1 (Thet Tin Nyunt

et. al., 2019), respectively, in the spectra of

Khamti amber. The absence of bands at 3048,

1642 and 887 cm–1 in the Raman spectrum

(Fig. 11, bottom) as well as in the IR spectrum

confirms that the Khamti material is amber and

(d)

(a)

(c)

(b)

Fig 5: Amber excavation at Laychun Maw: (a) Manual extraction of amber by manpower outside of the adit;

(b) amber with carbonaceous materials in limestone; (c) extracted amber and (d) yellowish brown honey

colour amber from Laychun Maw. (photos by Thet Tin Nyunt)


(a) (b)

(c) (d)

(a) (b)

Fig. 6: Nature of amber bearing limestone and amber production at Laychun Maw: (a-b) Entrance for adit of

the amber bearing limestone along the bedding plane where the amber is obtained; (c) The amber from amber

bearing limestone is transported by a pulley system (yellow bucket with rope and pulley); (d) Intercalation of

amber bearing limestone and carbonaceous materials, sometimes with sandstone. (photos by Thet Tin Nyunt)

Fig. 7: (a-b) Vertical shafts (1.2 m across, locally called Laybin) are also used to reach the amber bearing

limestone at Kyat Maw. (photos by Thet Tin Nyunt)


not copal (Brody et al., 2001; Wang et al., 2015;

compare also Liu, 2018).

8. Discussion and Conclusion

Gemmological properties of Khamti amber,

such as refractive index, specific gravity and

bright luminescence under LWUV illumination,

are quite similar to ambers from the Tanai and

Hti Lin regions. A difference consists in the

broad, O-H stretching related IR absorption

band around 3500 cm-1 (3420 cm-1 in our samples)

in the spectra of Khamti amber. This band is not

found in amber from Tanai and Hti Lin, and it

can be attributed to O-H stretching. In our

previous study (Tay et al., 2015), the analysis of

Tanai and Hti Lin amber was carried out with

only five samples each and the IR work was

focused at the range 3000 cm-1.

Thus, following the discovery of 3500 cm-1

absorption in Khamti amber, a preliminary

analysis of the Tanai and Hti Lin samples around

3500 cm-1 found that some samples appeared to

have a peak at 3500 cm-1 which we need to do

further analysis to confirm it. Therefore, consi-

dering the presence of carbonyl groups, this

hydroxyl can be assigned to carboxylic acid,

rather than molecular water in Khamti amber.

The characteristic FTIR and Raman spectra of

young copal have not been observed from the

Khamti amber which provides confirmation for

the older age of the amber i.e., mid-Cretaceous

(Albian) or older age as confirmed by the

Orbitolina sp. in the host limestone. Moreover, it

appears likely that Khamti amber was captured

and buried earlier or during the formation of the

mid-Cretaceous (Albian) limestone.

Fig. 8: (a) Twenty one analysed samples of amber for this research range from 0.45 ct (small brownish piece

at the left) to 2.49 ct (yellow sample at the centre). (photo by Tay Thye Sun); (b) Khamti ambers with different

colour varieties. (photos by Thet Tin Nyunt)(scale bars are 10 cm in length).


Fig. 9: Inclusions in Khamti amber: (a) Fly; (b) Mosquitoes?; (c) Spider; (d) Bird-Feather; (e) Spider; (f) Insect wings

and organic debris; (g) Mosquito; (h) Organic debris; (i) Parts of insects (j) Dragon fly? (k) Some parts of insects and

organic debris and (l) Ants and organic materials. (photomicrographs by Thet Tin Nyunt; dark field, 40×)

(j)

(e) (f)


Fig. 10: (a) Organic debris and gas bubbles; (b) Insect inclusions; (c) Organic debris; (d) Insect inclusion; (e-f) Plants,

other organic debris and gas bubbles in Khamti amber. (photomicrographs by Thet Tin Nyunt; dark field, 40×)

Fig. 11: Representative of IR absorption spectrum (top) and Raman spectrum (bottom) of Khamti amber

(modified after Thet Tin Nyunt et al., 2020). The asterisk in the IR spectrum marks an analytical artefact

(absorption by CO2 in the air). The Raman spectrum has been corrected for strong broad-band background

luminescence.


Acknowledgements

We are very thankful to the CCOP Technical

Committee for allowing us to present this article

in the CCOP 56th Annual Meeting Thematic

Session 2020. Sincere thanks are due to Khaing

Nan Shwe Gems & Jewellery Co. Ltd. for their

generous support. U Tin Kyaw Than (Principal,

Gemmological Science Centre, Myanmar) is

thanked for his advice during the present

research. We thank Andreas Wagner for sample

preparation, Dr. Eugen Libowitzky for help with

the FTIR–ATR analyses, and Prof. Dr. Lutz

Nasdala for help with Raman analyses. Much

appreciation to Daw Gjam, U Aung Naing, Dr.

Ko Hein and also the Yangon Gems and

Jewellery Entrepreneur Association (YGJEA)

for providing financial support that enabled lead

author Dr. Thet Tin Nyunt to present the results

of this study at the at the poster session of the 36th

International Gemmological Conference (IGC,

2019) in Nantes, France. Thanks, are also

contribute to Prof. Dr. Bo Wang, Director,

Nanjing Institute of Geology and Paleontology

and Dr. Jiang Tian, China University of

Geosciences (Beijing) for identification and

discussion on fossils. Last, but not least, the

assistance of Ko Min Thiha, Daw Yi Yi Win

(DGSE) and Daw Thuzar Tun (Yangon

University) in figure arrangements is gratefully

acknowledge.

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Copyright © 2021 by the Department of Mineral Resources of Thailand ISSN-2730-2695; DOI-10.14456/tgj.2021.7

Additional occurrence report on early Carboniferous radiolarians

from southern peninsular Thailand

Katsuo Sashida1*, Tsuyoshi Ito2, Sirot Salyapongse1 and Prinya Putthapiban1

1 Mahidol University Kanchanaburi Campus, 99 M.9 Lunsaum Kanchanaburi-Sangkraburi Road Sai Yok, Thailand 2 Institute of Geology and Geoinformation, Geological Survey of Japan, AIST, Tsukuba, 305-8567, Japan


Received 3 May 2021; Accepted 5 July 2021

Abstract

Moderately-preserved radiolarians have been identified from black chert interbedded with layers

of medium- to coarse-grained sandstone and variegated siliceous shale outcropped at a quarry near

Ka Bang, Songkhla Province, southern peninsular Thailand. The following radiolarians (13

species belonging to seven genera) were identified and systematically investigated: namely

Albaillella sp., Ceratoikiscum sp., Stigmosphaerostylus variospina, Stigmosphaerostylus cfr. vulgaris,

Stigmosphaerostylus cfr. delvolei, Stigmosphaerostylus sp., Stigmosphaerostylus? sp. A, Stigmosphae-

-rostylus? sp. B, Stigmosphaerostylus? sp. C, Trilonche? sp., Spongentactnia exilispina, Pylentonema

antiqia, and Archocyrtium sp. These radiolarians indicate the Tournaisian–Visean, Mississippian

(early Carboniferous) in age. The present authors have already reported a Tournaisian radiolarian

fauna which is slightly older than the present fauna from black bedded chert in the Saba Yoi-

Kabang area. This is an additional report on the occurrence of early Carboniferous radiolarians

from southern peninsular Thailand. The radiolarian-bearing chert reported in this study may have

been deposited in the upper continental rise to open deep-sea basins within the Paleotethys Ocean

on the basis of the lithological and radiolarian characteristics.

Keywords: Carboniferous, depositional setting, paleogeography, Paleotethys Ocean, radiolarian

fauna, Sibumasu terrane

1. Introduction

Mainland Thailand tectonically consists the

Sibumasu Terrane, Inthanon Zone, Sukhothai

Terrane, and Indochina Terrane, from west to

east (e.g., Metcalfe, 2017) (Fig. 1 A). Lower

Carboniferous siliceous rocks, such as chert and

siliceous shale, are distributed in southern

peninsular Thailand and the northwestern part of

peninsular Malaysia (e.g., Sashida, Salyapongse

and Charusri, 2002; Basir and Zaiton, 2011).

Several researchers have reported radiolarian

occurrences from these siliceous rocks (e.g.,

Caridroit, Fontaine, Jongkanjanasoontorn,

Suteethorn and Vachard, 1990; Sashida, Igo,

Hisada, Nakornsri and Ampornmaha, 1993;

Sashida, Igo, Adachi, Ueno, Nakornsri and

Sardsud, 1998; Sashida, Nakornsri, Ueno and

Sardsud, 2000; Sashida et al., 2002; Wonganan

and Caridroit, 2005; Wonganan, Randon and

Caridroit, 2007; Saesaengseerung, Sashida and

Sardsud, 2007a, 2007b, 2015; Kamata et al.,

2015). These radiolarian-bearing siliceous rocks

are considered to have been deposited on the

slope, upper continental rise, and lower

continental rise of the Sibumasu Terrane to the

ocean basin of the Paleotethys based on their

lithological characteristics and radiolarian faunal

analysis (Basir and Zaiton, 2011). The present

authors already reported the occurrence of early

Carboniferous radiolarians from the Saba Yoi-

Kabang areas, southern peninsular Thailand

(Sashida et al., 2002), and have continued to

investigate the area. A new radiolarian

assemblage, distinguishable from the previously-

reported one, was obtained from a chert layer

intercalated within the sandstone–siliceous shale

sequence cropping out in a quarry near the

locality of Sashida et al. (2002). Further, the

lower Carboniferous radiolarian-bearing sili-

ceous rocks shown in this study differ from

contemporary siliceous rocks in neighboring

areas (e.g., Sashida et al., 1993, 1998; Wonganan

et al., 2007) in containing coarse-grained clastic

materials. In this article, we describe an early


Katsuo Sashida et al. / Thai Geoscience Journal 2(2), 2021, p. 72-87 73

Carboniferous radiolarian assemblage from a

quarry near Ka Bang, southern peninsular

Thailand, as an additional occurrence report of

the authors’ previous study. In addition, we

discuss the depositional setting of the radiolarian-

bearing siliceous rocks.

2. Previous studies on southern peninsular

Thailand and sample locality of this study

Although most of peninsular Thailand is

included in the Sibumasu Terrane in the tectonic

subdivision map of mainland Southeast Asia by

Metcalfe (2017), southern part is in the Inthanon

Terrane (Fig. 1A).

Ueno and Charoentitirat (2011) summarized

the Carboniferous–Permian stratigraphy in

southern Peninsular Thailand (their Lower

Peninsular Thailand) and discriminated the

Yaha Formation (?Mississippian), Khuan Klang

Formation (Mississippian), Kaeng Krachan

Group (?latest Pennsylvanian–early Permian),

and Ratburi Limestone (early–late Permian).

Concerning the Yaha Formation, this formation

was first introduced by Muenlek, Meesook,

Tongchit, Tipdhonsab and Skulkaew (1985) in

the Geological Map of Changwat Narathiwat and

Amphoe Takbai for a mainly siliciclastic succes-

sion of shale, sandstone, siliceous shale, chert

and conglomerate (Ueno and Charoentitirat,

2011). Muenlek et al. (1985) also introduced the

Mayo Formation for similar lithologic characters

distributed in the North east of Yala and included

both formations in the Kaeng Krachan Group

with the Mayo Formation in the lower part and

the Yaha Formation in the upper. DMR (1999)

regarded the Mayo and Haya formations as

identical Carboniferous strata, and mapped the

Yaha Formation in Yala, Pattani, Songkhla and

Phatthalung provinces. Igo (1973) reported the

occurrence of late Tournaisian conodonts from a

chert–siliceous shale succession at the northern

end of Ko Yo in Songkhla Province which

substantiated the Mississippian age for the Yaha

Formation. Sashida et al. (2002) discriminated

Mississippian radiolarians from a sandstone–

chert succession exposed in the Saba Yoi-

Kabang area near the Songkhla-Yala provincial

boundary. Besides these Carboniferous fossils,

late Permian and Middle Triassic radiolarians

have been reported from two areas where the

distributional area of the Yaha Formation

according to DMR (1999): the Chana area

(Sashida et al., 2000) and the Rattaphum area

(Sardsud and Saengsrichan, 2002; Kamata et al.,

2008, 2009) in Songkhla Province. Ueno and

Charoentitirat (2011) regarded the Yaha Forma-

tion only provisionally as Mississippian due to

the controversial litho- and chronostratigraphic

characterization of the above mentioned Yaha

Formation. DMR (2013) discriminated 12

lithological units of Carboniferous sedimentary

rocks in Thailand and set up sandstone, shale,

siliceous shale with Posidonia becheri, chert,

and conglomerate around Songkhla and Yala,

in the border areas with Malaysia, as Unit Cy.

The Saba Yoi-Kabang area, study area of

this article, is located within the distributional

area of Unit Cy of DMR (2013) (Fig. 1B). A

study section crops out at the quarry along the

road, about 15 km west-southwest of Outcrop 1

of Sashida et al. (2002). A column of the section

with outcrop photographs is shown in Fig. 2.

Rocks at this outcrop strike N–S and dip 30° to

50° west. The total thickness of the formation of

this outcrop attains 12 m. Variegated siliceous

shale, mainly dark gray, green, brown, white,

yellow, and black, predominates in the section.

This siliceous shale is thinly bedded with

several millimeters to a few centimeter beds,

and it is strongly folded and sheared in the

middle part of the section. The folded and

sheared parts are cut by faults that are almost

parallel to the bedding. Sandstone beds in the

lower part intercalate with black chert beds and

have a total thickness of about 1.5 m. Sandstone

in the middle part of the section is coarse-

grained and thickly bedded with intercalated

very thin shale. Sandstone beds in the upper part

are thickly bedded and have about 2.5 m total

thickness. Radiolarian-bearing chert is thinly

bedded with intercalated thin siliceous shale,

and the total thickness is about 30 cm. This chert

is black when fresh and brown to yellow on

weathered surfaces. The lower and upper limits

of this section are not exposed.

3. Materials and methods

We collected more than 10 samples from

variegated siliceous shale and other chert layers

of the section. Among them, only one sample

74 Katsuo Sashida et al. / Thai Geoscience Journal 2(2), 2021, p. 72-87

(SYK-1) yielded radiolarians. Under thin section,

the samples characteristically contain radiolarian

and foraminifer shells within matrices consisting

of fine-grained quartz and clay minerals (Fig. 3).

Foraminiferal shells are concentrated in some

parts and their maximum diameter attains 300

μm. The foraminiferal shells were replaced by

silica and are infilled with silica.

Radiolarian specimens were extracted from

chert by the procedures, which generally

established by Pessagno and Newport (1972), as

mentioned below. In addition, we recovered the

foraminiferal shells during the procedures.

Crushed chert of several centimeters size was

soaked in a diluted hydrofluoric acid (HF)

solution (3–5%) for about 24 hours at room

temperature. The sample was washed and sieved

by nylon mesh of 36 μm for collecting residue.

This procedure was repeated five times for every

samples. The residue was dried in an oven. Well-

preserved specimens in the residue were placed

on scanning electron microscopy (SEM) plugs

and coated with platinum in a vacuum evapo-

rator. SEM images of foraminifers are shown in

Fig. 4; those of radiolarians are shown in Figs. 5

and 6. Generic and species name of the forami-

nifers have not been identified. The systematic

paleontology of radiolarians will be described in

Section 6.

4. Age of radiolarian fauna

We discriminated radiolarians of 13 species

belonging to seven genera from the chert sample

(SKY-1). Identified radiolarians are Albaillella

sp., Ceratoikiscum sp., Stigmosphaerostylus

variospina (Won), Stigmosphaerostylus cfr.

delvoli (Gourmelon), Stigmosphaerostylus cfr.

vulgaris (Won), Stigmosphaerostylus sp.,

Stigmosphaerostylus? sp. A, Stigmosphaero-

stylus? sp. B, Stigmosphaerostylus? sp. C,

Trilonche? sp., Spongentactnia exilispina (Fo-

reman), Pylentonema antiqua (Deflandre), and

Archocyrtium sp.

Stigmosphaerostylus vulgaris and Stigmos-

phaerostylus variospina was originally described

by Won (1983) from the lower Carboniferous the

Rheinisches Schiefergebirge, Germany. Subsequ-

ently, Gourmelon (1987) reported these two

species from the Tournaisian of the Montagne

Noire and the central Pyrenees in France.

Saesaengseerung et al. (2007a) reported the

occurrence of these two species from a sequence

of chert, siliceous shale, and sandstone from the

Pak Chom area, Loei Province, northeastern

Thailand. The occurrence of these two species

has been reported by Sashida et al. (2002) from

the Saba Yoi-Kabang area. Stigmosphaerostylus

delvoli was first reported from the Tournaisian of

the Montagne Noire and Central Pyrenees by

Gourmelon (1987). Spongentactinia exlispina

was described as Entactinia exlispina by

Foreman (1963) from the Upper Devonian Ohio

Shale. Subsequently this species was reported

from the Tournaisian of the Montagne Noire by

Gourmelon (1987). Pylentonema antiqua was

first described from the lower Carboniferous of

France by Deflandre (1963) and subsequently

Holdsworth (1973) and Holdsworth, Jones and

Allison (1978) reported this species from the

Upper Devonian of Alaska and the lower

Carboniferous of Istanbul, Turkey, respectively.

Sandberg and Gutshik (1984) reported this

species from the Mississippian (lower

Carboniferous) of North America. This species is

also known from the Montagne Noire, France

(Gourmelon, 1987), Southern Thailand (Sashida

et al., 2002), and northwestern Peninsular

Malaysia (Basir and Zaiton, 2011).

We discriminate poorly preserved species

Albaillella sp. whose shell features are slightly

similar to Albaillella indensis Won. According to

Aitchison, Suzuki, Caridroit, Danelian and Noble

(2017), Albaillella idensis has a range from the

late Tournaisian to middle Visean (Mississip-

pian) and this species is an index of the boundary

between the upper Tournaisian through lower

Visean. As mentioned above, our radiola-

rian fauna is similar to those from the lower

Carboniferous Rheinisches Schiefergebirge,

Germany (Won, 1983) and the Montagne Noire,

France (Gourmelon, 1987).

The geologic age of the chert sample (SKY-1)

may be late Tournaisian to early Visean

(Mississippian). In our previous study, Albaillella

deflandrei Gourmelon occurred in all of the

samples (Sashida et al., 2002). Albaillella deflan-

drei is regarded as an index species of the late

middle Tournaisian by Aitchison et al. (2017);

therefore, our present radiolarian is younger than

the samples from our previous study.


Fig 1: Location map of our study area. A. tectonic subdivision of Thailand and study area. The base map

is modified from Metcalfe (2017). B. Location map of our study area, SKY-1, our examined sample. The

basic geologic map is modified from DMR (2013).

Fig 2: Columnar section and outcrop photos of study section.


Fig 3: Thin section microphotographs of radiolarian-bearing chert. 1, 3, and 4 are under

plane polarized light; 2 is under cross polarized light.

Fig 4: SEM (Scanning Electron Microscope) photos of foraminiferal shells.


Fig 5: Radiolarian SEM photos of Mississippian chert from southern peninsular Thailand. All scale bars

indicate 100 μm. 1, 3, 4. Albaillella sp., 1, EES-KS-ST-0001, 3, EES-KS-ST-0003, 4, EES-KS-ST-0004, 2,

20. Ceratoikiscum sp., 2, EES-KS-ST-0002, 20, EES-KS-ST-0020, 5, 6, 7. Trilonche? sp., 5, EES-KS-ST-

0005, 6, EES-KS-ST-0006, 7, EES-KS-ST-0007, 8, 9. Stigmosphaerostylus sp., 8, EES-KS-ST-0008, 9, EES-

KS-ST-0009, 10, 14, 17, 18. Stigmosphaerostylus? sp. A, 10, EES-KS-ST-0010, 14, EES-KS-ST-0014, 17,

EES-KS-ST-0017, 18, EES-KS-ST-0018, 11. Stigmosphaerostylus variospina (Won), EES-KS-ST-0011, 12.

Stigmosphaerostylus cfr. vulgaris (Won), EES-KS-ST-0012, 13. Stigmoshpaerostylus? sp. B, EES-KS-ST-

0013, 15. Stigmoshpaerostylus? sp. C, EES-KS-ST-0015, 16. Stigmoshpaerostylus cfr. delvolei (Gourmelon),

EES-KS-ST-0016, 19. Spongentactinia exillispina (Foreman), EES-KS-ST-0019.


Fig 6: Radiolarian SEM photos of Mississippian chert from southern peninsular Thailand. All scale bars

indicate 100 μm. 1–15. Pylentonema antiqua Deflandre, 1, EES-KS-ST-2001, 2, EES-KS-ST-2002, 3, EES-

KS-ST-2003, 4, EES-KS-ST-2004, 5, EES-KS-ST-2005, 6, EES-KS-ST- 2006, 7, EES-KS-ST-2007, 8, EES-

KS-ST-2008, 9, EES-KS-ST-2009, 10, EES-KS-ST-2010, 11, EES-KS-ST-2011, 12, EES-KS-ST-2012, 13,

EES-KS-ST-2013, 14, EES-KS-ST-2014, 15, EES-KS-ST-2015, 16. Archocyrtium sp., EES-KS-ST-2016.


5. Depositional environment of radiolarian-

bearing chert

This article reports the late Tournaisian to

early Visean (Mississippian) radiolarians from the

chert in the Inthanon Zone. Middle–Late

Devonian and early Carboniferous radiolarians

have been reported from the “Fang Chert”

distributed in north of Chiangmai, within the

Inthanon Zone (e.g., Ueno, 1999) northern

Thailand (Sashida et al., 1993, 1998; Wonganan

et al., 2007). These siliceous rock sequence

basically does not contain any coarse-grained

clastic materials and they are thought to have been

deposited in the offshore, far from land and deeper

environments of the Paleotethys Ocean (Wong-

anan et al., 2007). In contrast, the radiolarian-

-bearing chert is intercalated in the medium to

coarse-grained sandstone as described by Sashida

et al. (2002) and the present study (Fig. 2). The

presence of sandstone beds indicates that the

depositional site is near the continent, not far from

land. Furthermore, the chert sample (SYK-1)

contains foraminiferal shells (Figs. 3 & 4), suggest-

ing that depth of chert accumulation is not deeper

than a carbonate compensation depth. Saesaeng-

seerung et al. (2015) discriminated detrital quartz

grains in siliceous shale distributed in the Uthai

Thani area which means that Devonian to lower

Carboniferous radiolarian-bearing siliceous shale

has been deposited in hemipelagic, not pelagic

Fig 7: Image of depositional environment of radiolarian bearing siliceous sedimentary rocks. A

Paleogeographic map at Mississippian (Tournaisian–Visean: (340 Ma). Map is modified from

Metcalfe (2017). B. Image of the depositional sites of radiolarian-bearing sediments across the

Paleotethys Ocean. (a): Sashida et al. (2002), Saesaengseerung et al. (2015), The present study. (b):

Feng et al. (2004), (c): Sashida et al. (1998), Wonganan and Caridroit (2005), Wonganan et al. (2007),

(d): Saesaengseerung et al. (2007a), L=Lhasa, SQ= South Qiangtang, WC=Western Cimmerian

Continent,

Continent,


environment. For these reasons, we speculate that

the radiolarian-bearing chert of Sashida et al.

(2002) and this study deposited on shallower area

near land.

In addition to the above-mentioned charac-

teristics, the radiolarian faunal characteristic

supports the speculation of the depositional

setting. Catalano, Stefano and Kozur (1991), Feng

and Ye (1996), Feng, Helmcke, Chonglakmani,

Helmcke and Liu (2004), and others mentioned

that early Carboniferous radiolarian assemblages

from shallow-water sediments are scarce and low

diverse: only by members of the Spumellaria

and/or Entactinaria usually represented. On the

other hand, early Carboniferous radiolarian

assemblages from deep-water basins are charac-

terized by abundant and high diversity radiola-

rians including Spumellaria and/or Entactinaria,

Nassellaria, and Albaillellaria, and they usually

make radiolarites and/or radiolarian chert. Basir

and Zaiton (2011) reported the occurrence of early

Carboniferous (Tournaisian) radiolarians from

Peninsular Malaysia. They discriminated following

three radiolarian assemblages based on the faunal

composition and lithology: the Stigmosphaero-

stylus, Archocyrtium, and Albaillellara assem-

blages. The Stigmosphaerostylus Assemblage is

characterized by the occurrence of Stigmos-

pharostylus variospina and spherical entactina-

rians but its specific diversity is very low. The

Archocytrium Assemblage is characterized by

moderate diversity and is dominated by cone-

shaped archocyrtiids such as Archocyrtium. This

assemblage consists of 20 radiolarian species. The

Albaillella assemblage is characterized by the

common occurrence of Albaillella and high

species diversity (more than 34 species identified).

Basir and Zaiton (2011) inferred that The

Stigmosphaerostylus Assemblage is due to the

shallow water environment (upper continental

rise), the Archocyrtium Assemblage is rather

deeper environment (continental rise), and the

Abaillella Assemblage is open deep-sea marine

environment (Ocean basin). They recognized the

radiolarian absence in the fauna is attributed to a

strong diagenesis and selective dissolution

(O’Dogherty, Rodriguez-Canero, Gursky, Matin-

Algarra, and Caridroit, 2000). Our examined

radiolarian fauna from the chert sample is

correlated to the transitional assemblage between

the Arhcocyrtium and Albaillella assemblages

based on radiolarian faunal similarity, implying

that the chert has been deposited in the upper

continental rise to the open deep-sea marine

environment (Ocean basin).

The depositional sites of the Devonian to

lower Carboniferous radiolarian-bearing siliceous

rocks in Thailand are located in roughly four sites

in the Paleotethys Ocean based on the lithological

characteristics and present geological settings

(Fig. 7). The radiolarian-bearing chert reported in

this study may have been deposited in the upper

continental rise to the open deep-sea basins within

the Paleotethys Ocean on the basis of the

lithological and faunal characteristics. Seamount

consisting of basaltic rocks and carbonate rocks

completely lacks of coarse-grained terrestrial

materials which may indicate that it formed far

from land in the Paleotethys Ocean.

6. Systematic paleontology

Radiolarian description was made by K. S.

and T. I. All specimens treated in this paper are

stored at the Earth Evolution Sciences, University

of Tsukuba, Japan with registered EES-KS.

Taxonomic scheme of radiolarians is followed

from that of Noble et al (2017).

Order Albaillellaria Deflandre, 1953

Family Albaillellidae Deflandre, 1953 sensu

Holdsworth (1977)

Genus Albaillella Deflandre, 1952

Type species. - Albaillella paradoxa Defladre,

1952

Albaillella sp.

Figs. 5.1, 5.3, 5.4

Remarks. -We collected more than 10 specimens

attributed to this species. However, all of them are

poorly preserved. Our examined specimens may

have cylindrical shell with a smooth surface and

conical apical part, and a well-developed H-frame.

At the pseudo-abdomen, ventral and dorsal wing

may be present. Although we cannot compare

precisely our specimens, their outer shell features,

short conical and short wing are slightly similar to

those of Albaillella indensis Won. Our specimens

may be distinguished from Albaillella deflandre

Gourmelon by having above mentioned shell

characters.


Sample, occurrence, and range. - This species

occurs from Sample SKY-1 and is known from

southern Thailand. Mississippian (Tournaisian–

Visean).

Family Ceratoiksicidae Holdsworth, 1969

Genus Ceratoikiscum Deflandre, 1953

Type species. - Ceratoikiscum avimexpectans

Deflandre, 1953

Ceratoikiscum sp.

Figs. 5.2, 5.20

Remarks. - Three incomplete specimens were

examined. Our specimens are characterized by

having a sturdy and conical a.a (a-rod: extra-

triangular) and long needle-like i.d (intersector:

extratriangular), i.v. (intersetor: extratriangular)

and a.p. (a-rod: extratriangular) (nomenclature of

Ceratoikiscum is from Holdsworth, 1969).

However, cavaeal ribs are not clear which may be

covered by spongy patagial structure.

Sample, occurrence, and range.- This species



Visean).

Order Entactinaria Kozur and Mostler, 1982

Family Entactiniidae Riedel, 1967

Genus Spongentactinia Nazarov, 1975

Type species. - Spongentactinia fungosa Nzarov,

1975

Spongentactinia exilispina (Foreman, 1963)

Fig. 5.19

1963 Entactinia exilispina Foreman, p. 273, pl. 1,

fig. 8.

1987 Spongentactinia exilispina (Foreman),

Gourmelon, p. 56, 57, pl. 5, figs. 6-8.

Remarks. - We identified only one specimen of

this species. Our specimen is characterized by

having a spongy spherical shell with may be six

spines which are three bladed. Although our

examines specimen is an incomplete one, general

outer shell features are identical to those of

S. exilispina.



Ohio shale and Montagne Noire, France. Upper

Devonian (Famennian) to Mississippian

(Tournaisian–Visean).

Genus Stigmosphaerostylus Rüst, 1892

Type species. - Stigmosphaerostylus notabilis

Rüst, 1892

Stigmosphaerostylus variospina (Won, 1983)

Fig. 5.11

1983 Palaeoxyphostylus variospina Won, p. 156,

156, pl. 8, figs. 1–4, 6–22.

1986 Entactinia variospina (Won), Gourmelon,

pl. 4, fig. 1.

1987 Entactinia variospina (Won), Gourmelon, p.

49, 50, pl. 3, figs.6, 11.

1989 Entactinia variospina (Won), Braun, p. 368,

pl. 2, figs. 3, 4, pl. 4, fig. 5.

1990 Entactinia variospina (Won), Braun, pl. 7,

figs. 4.1–4.13, 4.14.

1994 Entactinia variospona (Won), Kiessling and

Tragelehn, p. 236, pl. 4, figs. 23, 24.

1995 Entactinia variospina (Won), Basir, p. 78,

pl. 1, figs.2–4.

1996 Entactinia variospina (Won), Spiller, pl. 2,

figs. 7, 8.

1997 Entactinia variospina (Won), Feng et al., p.

86, pl. 3, figs. 12, 13.

1998 Entactinia variospina (Won), Sashida et al.,

p. 13, 15, figs. 9.1–9.10.

1998 Entactinia variospina (Won), Wang et al.,

pl. 2, figs. 6, 7.

1998 Entactinia variospina (Won), Won, p. 238,

pl. 2, fig. 18.

2000 Entactinia variospina (Won), Sashida et al.,

p.83, figs. 6.5–6.12.

2002 Stigmosphaerostylus variospina (Won),

Spiller, p. 43, pl. 6, figs. g, h, i.


Sashida et al., p. 132, 133, pl. 1, figs.

18,22,23, pl. 3, fig.12?

2007a Stigmosphaerostylus variospina (Won),

Saesaengseerung et al., p. 115, 116, figs.

8,7, 8.8, 8.17.


Basir and Zaiton, pl. 1, figs. 1–4.


Saesaengseerung et al., p. 123, pl. 2, figs. 1–14.


Remarks. - Only one specimen was examined.

Our specimen has a spherical shell with short, and

sturdy six spines. Shell has many small circular

pores surrounded by pentagonal to circular shell

frames. Length of spines is generally half of the

shell diameter. Won (1983) showed the various

types of the spines; number, shape and length of

this species. Our examined specimen has shorter

and more sturdy spines compared with any of her

examined specimens. Gourmelon (1987) also

showed several shell morphology of this species.

Our specimen is similar to his specimens (pl. 3,

figs. 7, 8) which have shorter spines. Our

specimen is also similar to the species reported by

Saesaengseerung et al. (2007) by having short and

sturdy three-bladed spines. This species is

distinguished from E. vulgaris by having above

mentioned shell characters.



northern and southern Thailand, Peninsular

Malaysia, Europe, and South China. Upper

Devonian (Famennian) to Mississippian

(Tournaisian–Visean).

Stigmosphaerostylus cfr. delvolei (Gourmelon, 1987)

Fig. 5.16

cfr.

1987 Entactinia? delvolvei Gourmelon, p. 45, 46,

pl. 7, figs. 8–10.

Remarks. - Two specimens attributed to this

species have been identified. Examined

specimens characteristically have a spherical shell

with 6 to 7? thin and long spines with small

needle-like bi-spines. Illustrated specimen has a

long and thin spine whose length is almost twice

as the diameter of a spherical shell. Our specimens

are similar to the type species of this species which

has only two long spines. Our specimens are

incomplete, therefore we identified this species

with cfr.



the Montagne Noire, France. Mississippian

(Tournaisian).

Stigmosphaerostylus cfr. vulgaris (Won, 1983)

Fig. 5.12

cfr.

1983 Entactinia? vulgaris Won, pl. 4, figs. 1-3

1986 Entactinia vulgaris Won, Gourmelon, p.

184, pl. 2, fig. 4.

1987 Entactinia vulgaris Won, Gourmelon, p.

50, 51, pl. 4, figs. 1-6.

Remarks. - We examined two specimens. An

illustrated specimen has a spherical shell with 6

three-bladed long conical spines. Many small

circular pores surrounded by pentagonal to

circular frames are present on the surface of the

shell. The original specimens attributed to this

species by Won (1983) have more sturdy and

longer spines. Therefore, we put cfr. for our

specimens.



Germany and France, Mississippian (Tournaisian–

Visean).

Stigmosphearostylus sp.

Figs. 5.8, 5.9

Remarks. - Several incomplete specimens were

examined. Illustrated specimens have a rather

small spherical shell with may be six or seven

spines. Small circular pores surrounded by square

to circular pore frames are present. Thin to

moderately thick internal spicule systems

consisting of six-rayed spicules are observed in

our specimens. Internal spicule system does not

have median bar, point centered. This species is

distinguished from S. sp. B of the present study by

having smaller spherical shell.




Visean).

Stigmosphaerostylus? sp. A

Figs. 5.10, 5.14, 5.17, 5.18

Remarks. - Seven specimens of this species were

examined. This species has a spherical shell with

six, short, three-bladed and conical spines. This


species is similar to S. deflendrei (Won, 1991)

described from Germany in general shell feature.

However, latter species has longer and more

sturdy spines. This species also resembles S.

vulgaris (Won, 1983), but it differs from the latter

by smaller and shorter spines. We questionably

assigned this species in Stigmosphaerostylus

because the internal shell structure cannot be

detected.




Visean).

Stigmosphaerostylus? sp. B

Fig. 5.13

Remarks. – One specimen has been identified.

This species is characterized by a spherical shell

with may be six or seven spines. Spherical shell is

thick and has many and small circular pores on its

outer surface. Small conical spines are present at

the junction of each neighboring pore flame.

Spines are three-bladed and sturdy and long

conical shale. We cannot observe the inner side of

the spherical shell and determine the presence of

spicule system or inner shell. Therefore, we

questionably assigned this species in Stigmosph-

earostylus. This species is distinguished from

Stigmosphearostylus? sp. A of the present study

by having longer and more sturdy spines.




Visean).

Stigmosphaerostylus? sp. C

Fig. 6.15

Remarks. – Only one specimen has been

examined. This species has a spherical shell with

more than four spines whose length is almost two-

thirds of the diameter of shell. Shell has many

small circular pores surrounded by polygonal to

circular frames. This species similar to Stigmos-

phaerostylus? sp. A of the present study but it has

thicker spines.




Visean).

Genus Trilonche Hinde, 1899 sensu Aitchison

and Stratford, 1997

Type species.- Trilonche vetusta Hinde, 1899

Trilonche? sp.

Figs. 6.5, 6,7

Remarks. - Three specimens were examined. This

species has a spherical shell with three to more

three-bladed spines and an internal spherical shell.

Inner and outer shells are connected by six three-

bladed thick spines. The presence of an internal

spicule system cannot be determined. The outer

shell is thick and has many small pores on the

surface of the outer shell. The internal surface of

the outer shell is fine sponge. Inner shell has a

circular phylome. We questionably placed this

species in Trilonch because we did not observe the

internal spicules in the inner shell and the inner

shell has a pylome.




Visean).

Family Pylentonemidae Deflandre, 1963

Genus Pylentonema Deflandre, 1963 sensu

Holdsworth et al., 1978

Type species.- Acanthopyle antiqua Deflandre,

1960

Pylentonema antiqua (Deflandre, 1960)

Figs. 6.1–6.15

1960 Acanthopyle antiqua Deflandre, p. 216, pl.

1, fig. 14

1963 Pylentonema antiqua (Deflandre), p. 3981–

3984, figs. 1–5.

1973 Pylentonema antiqua (Deflandre), Holds-

worth, p. 122-125, pl. 1, fig. 4.

1978 Pylentonema antiqua (Deflandre), Holds-

worth et al, p. 785, figs. 3d, 3e.

1984 Pylentonema antiqua (Deflandre), Sandberg

and Gutshick, pl. 6, figs. P, T.

1986 Pylentonema antiqua (Deflandre), Gourme-

lon, p. 188-189, pl. 1, figs. 7, 8.


1987 Pylentonema antiqua (Deflandre), Gourme-

lon, p. 102, pl. 15, figs. 1–6.

1998 Pylentonema antiqua (Deflandre), Won, p.

255, 256, pl. 6m figs. 9–14, 16.

2002 Pylentonema antiqua (Deflandre), Sashida

et al., P. 131, 132, pl. 1, figs. 14–17, 20–22,

pl. 2, fig. 2, pl. 3, figs. 2, 6, 8, 9, 11?.

Remarks. - More than 30 specimens identified to

this species have been obtained. Our forms are

characterized by having a spherical shell with 7

spines, among which one is generally small and

others are three bladed and sturdy, and their length

is almost same as the diameter of spherical shell.

Small circular pores surrounded by pentagonal to

circular pore rim are present. Internal surface of

spherical sell is generally spongy. A large circular

pylome is present surrounded by a narrow pylome

rim. We can see the internal spicule system (e.g.,

fig. 6.6), but the presence of inner shell is not sure

due to the mesh structure of the internal surface of

spherical shell. Position of spines around pylome

is variable as discussed by Won (1998), but the

type of four spines around pylome (her type Bs

and Bd) may be most predominate.


obtained from Sample SKY-1 and is known from

Germany, France, North America, Turkey,

Thailand. Upper Devonian (upper Famennian) to

Mississippian (Tournaisian–Visean).

Order Nassellaria Ehrenberg, 1875

Family Archocyrtidae Kozur and Mostler, 1981

Genus Archocytrium Deflandre, 1972 sensu

Holdsworth (1973)

Type species. - Archocyrtium riedeli Deflandre,

1960

Archocyrtium sp.

Fig. 6.16

Remarks. - Three specimens attributed this species

were identified. An illustrated specimen has a

subspherical cephalis with three bladed apical

horn and three three-bladed feet. Length of apical

horn is almost equal with the diameter of cephalis.

Small pores are observed on the surface of

cephalis. Length of three feet are not known. Our

specimens may have week pyrome. This species

is similar to Arhocyrtium venustum Cheng and A.

riedeli Deflandre, however, precise comparison

cannot be made.




Visean).

7. Conclusions

1. Radiolarians of 13 species belonging to

seven genera have been identified from a

black chert bed intercalated within

sandstone and variegated siliceous shale

at the Kabang area, Songkhla Province,

southern peninsular Thailand.

2. The age of the radiolarians may indicate

the Tournaisian to Visean, Mississippian

(early Carboniferous). The age is slightly

younger than that of the previously

reported radiolarians in the Saba Yoi-

Kabang area in our previous study.

3. The radiolarian-bearing chert character-

ristically contains foraminiferal shells

and therefore the chert may have been

deposited in shallower ocean than the

carbonate compensation depth. The chert

is intercalated within sandstone beds, so

that the chert was deposited near land.

4. The radiolarians from the chert sample is

correlated to the transitional assemblage

between the Arhcocyrtium and Albail-

lella assemblages. Consequently, the

chert has probably been deposited in the

upper continental rise to the open deep-

sea marine environment.

5. On the basis of the lithological and

radiolarian faunal characteristics, the

radiolarian-bearing chert may have been

deposited in the upper continental rise to

the open deep-sea basins within the

Paleotethys Ocean. However, further

study such as sedimentary structure and

zircon provenance analyses are required

to clarify this interpretation.

Acknowledgements

The first author (K.S.) would like to express

his sincere thanks to the Mahidol University

Kanchanaburi Campus for offering facilities to


carry out our research. The authors also thank to

Drs. Sardsud, A. and Saesaengseerung, D. of the

DMR (Department of Mineral Resources of

Thailand) for giving us various suggestions for

our investigations in Thailand. The authors

further express our thanks to Dr. Suzuk N. of the

Tohoku University for offering important

radiolarian literature. We would like to

acknowledge three anonymous reviewers for

critical reading the manuscript and giving us

many constructive suggestions that improved

our manuscript.

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Dr. Ian Watkinson

Mr. Jittisak Premmanee

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Assoc. Prof. Dr. Lindsay Zanno

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Dr. Pol Chaodumrong

Dr. Pradit Nulay

Dr. Prinya Putthapiban


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Assoc. Prof. Dr. Sachiko Agematsu-Watanabe

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Dr. Seung-bae Lee

Dr. Siriporn Soonpankhao

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Mr. Somchai Chaisen

Dr. Surin Intayos

Mr. Sutee Chongautchariyakul

Dr. Tawatchai Chualaowanich

Mr. Thananchai Mahatthanachai

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Mr.Tritip Suppasoonthornkul

Dr. Weerachat Wiwegwin

Assoc. Prof. Dr. Yoshihito Kamata

Chiang Mai University, Thailand


Universiti Kebangsaan Malaysia, Malaysia


Prince of Songkla University, Thailand

Coordinating Committee for Geoscience Programmes in East and

Southeast Asia, Thailand (CCOP)

University of London, England


Fukuoka University, Japan

Mahidol University, Kanchanaburi campus, Thailand

University of Tsukuba, Japan

Kingsborough Community College, City University of New York, USA

Yamaguchi University, Japan

Khon Kaen University, Thailand

North Carolina State University, USA


Global Geoscience, British Geological Survey, UK

Western Colorado University, Thailand

Chulalongkorn University, Thailand


University of California, Riverside, USA



Kasetsart University, Thailand

Department of Mineral Fuels, Thailand


Geological Society of Thailand, Thailand


Mahidol University Kanchanaburi Campus, Thailand


Suranaree University of Technology, Thailand




Korea Institute of Geoscience and Mineral Resources, Republic of Korea


Geo-Informatics and Space technology Development Agency, Ministry of

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Burapha University, Chanthaburi Campus, Thailand





Retired geophysicist, Japan





Vol. 2 No. 2

July 2021

ISSN 2730-2695

C O N T E N T S

Honorary Editors

Dr. Sommai Techawan

Mr. Niwat Maneekut

Mr. Montri Luengingkasoot

Dr. Young Joo Lee

Advisory Editors


Dr. Dhiti Tulyatid




Associate Editors



Assoc. Prof. Dr. Kieren Torres Howard


Dr. Mongkol Udchachon



Published by



Coordinating Committee for

Geoscience Programmes in

East And Southeast Asia (CCOP) Copyright © 2021 by the Department of Mineral Resources of Thailand


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Katsuo Sashida, Tsuyoshi Ito, Sirot Salyapongse, and Prinya Putthapiban

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Dr. Apsorn Sardsud

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